Add ETCD_ENDPOINTS env var support

[TejasNaikk]

Test :

NODE_NAME=controller-1 RUNTIME_ENV=gating ETCD_ENDPOINTS=http://localhost:2379 mvn spring-boot:run -Dspring-boot.run.arguments="--server.port=8081"
[INFO] Scanning for projects...
[INFO]
[INFO] --------------< io.clustercontroller:cluster-controller >---------------
[INFO] Building cluster-controller 0.1.0-SNAPSHOT
[INFO]   from pom.xml
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] >>> spring-boot:3.1.5:run (default-cli) > test-compile @ cluster-controller >>>
[INFO]
[INFO] --- resources:3.3.1:resources (default-resources) @ cluster-controller ---
[INFO] Copying 1 resource from src/main/resources to target/classes
[INFO]
[INFO] --- compiler:3.11.0:compile (default-compile) @ cluster-controller ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- resources:3.3.1:testResources (default-testResources) @ cluster-controller ---
[INFO] skip non existing resourceDirectory /Users/tjnaik/Uber/cluster-controller/src/test/resources
[INFO]
[INFO] --- compiler:3.11.0:testCompile (default-testCompile) @ cluster-controller ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] <<< spring-boot:3.1.5:run (default-cli) < test-compile @ cluster-controller <<<
[INFO]
[INFO]
[INFO] --- spring-boot:3.1.5:run (default-cli) @ cluster-controller ---
[INFO] Attaching agents: []
11:29:22.700 [main] INFO io.clustercontroller.ClusterControllerApplication -- Starting Multi-Cluster Controller Application with REST APIs

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v3.1.5)

2026-01-14T11:29:22.900-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Starting ClusterControllerApplication using Java 21.0.7 with PID 84491 (/Users/tjnaik/Uber/cluster-controller/target/classes started by tjnaik in /Users/tjnaik/Uber/cluster-controller)
2026-01-14T11:29:22.901-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : No active profile set, falling back to 1 default profile: "default"
2026-01-14T11:29:23.403-08:00  INFO 84491 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8081 (http)
2026-01-14T11:29:23.407-08:00  INFO 84491 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2026-01-14T11:29:23.407-08:00  INFO 84491 --- [           main] o.apache.catalina.core.StandardEngine    : Starting Servlet engine: [Apache Tomcat/10.1.15]
2026-01-14T11:29:23.448-08:00  INFO 84491 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2026-01-14T11:29:23.448-08:00  INFO 84491 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 523 ms
2026-01-14T11:29:23.520-08:00  INFO 84491 --- [           main] i.c.config.ClusterControllerConfig       : Loading config from classpath: application.yml
2026-01-14T11:29:23.530-08:00  INFO 84491 --- [           main] i.c.config.ClusterControllerConfig       : Successfully loaded configuration from classpath (application.yml)
2026-01-14T11:29:23.530-08:00  WARN 84491 --- [           main] i.c.config.ClusterControllerConfig       : Failed to get etcd.endpoints from config: EnvironmentUtils not initialized yet
2026-01-14T11:29:23.530-08:00  INFO 84491 --- [           main] i.c.config.ClusterControllerConfig       : Loaded cluster controller config - etcd endpoints: http://localhost:2379, task interval: 30s
2026-01-14T11:29:23.530-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Loaded configuration
2026-01-14T11:29:23.532-08:00  INFO 84491 --- [           main] i.c.store.EtcdPathResolver               : EtcdPathResolver initialized
2026-01-14T11:29:23.532-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing cluster-agnostic MetadataStore connection to etcd
2026-01-14T11:29:23.631-08:00  WARN 84491 --- [           main] i.n.r.d.DnsServerAddressStreamProviders  : Can not find io.netty.resolver.dns.macos.MacOSDnsServerAddressStreamProvider in the classpath, fallback to system defaults. This may result in incorrect DNS resolutions on MacOS.
2026-01-14T11:29:23.686-08:00  INFO 84491 --- [           main] i.c.store.EtcdMetadataStore              : EtcdMetadataStore initialized with endpoints: http://localhost:2379 and nodeId: controller-1
2026-01-14T11:29:23.686-08:00  INFO 84491 --- [           main] i.c.store.EtcdMetadataStore              : Coordinator goal state path configured to group='coordinators', unit='default-coordinator'
2026-01-14T11:29:23.686-08:00  INFO 84491 --- [           main] i.c.store.EtcdMetadataStore              : Initialize called - already done in constructor
2026-01-14T11:29:23.686-08:00  INFO 84491 --- [           main] i.c.store.EtcdMetadataStore              : Skipping single-cluster leader election - using MultiClusterManager for distributed coordination
2026-01-14T11:29:23.686-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : MetadataStore initialized successfully
2026-01-14T11:29:23.694-08:00  INFO 84491 --- [           main] i.c.m.lock.DistributedLockManager        : DistributedLockManager initialized
2026-01-14T11:29:23.696-08:00  INFO 84491 --- [           main] i.c.m.registry.ControllerRegistry        : ControllerRegistry initialized
2026-01-14T11:29:23.696-08:00  INFO 84491 --- [           main] i.c.m.registry.ClusterRegistry           : ClusterRegistry initialized
2026-01-14T11:29:23.698-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing TemplateManager for multi-cluster support
2026-01-14T11:29:23.699-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing IndexManager for multi-cluster support with template support
2026-01-14T11:29:23.701-08:00  INFO 84491 --- [           main] i.c.metrics.MetricsProvider              : MetricsProvider initialized for the controller: controller-1
2026-01-14T11:29:23.701-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing ShardAllocator
2026-01-14T11:29:23.704-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing ActualAllocationUpdater
2026-01-14T11:29:23.705-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing GoalStateOrchestrator with RollingUpdateOrchestrationStrategy
2026-01-14T11:29:23.705-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing Discovery for multi-cluster support
2026-01-14T11:29:23.706-08:00  INFO 84491 --- [           main] i.c.ClusterControllerApplication         : Initializing shared TaskContext for multi-cluster support
2026-01-14T11:29:23.708-08:00  INFO 84491 --- [           main] i.c.m.lifecycle.ClusterLifecycleManager  : ClusterLifecycleManager initialized (controller: controller-1, health check interval: 10s)
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : MultiClusterManager initialized: controllerId=controller-1
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : ========================================
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : Starting MultiClusterManager
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : Controller ID: controller-1
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : ========================================
2026-01-14T11:29:23.710-08:00  INFO 84491 --- [           main] i.c.m.registry.ControllerRegistry        : Registering controller: controller-1
2026-01-14T11:29:23.846-08:00  INFO 84491 --- [           main] i.c.m.registry.ControllerRegistry        : ✓ Controller registered: controller-1 (leaseId: 7587892186338506205)
2026-01-14T11:29:23.852-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : Discovered 3 clusters: [cluster-gamma, cluster-alpha, cluster-beta]
2026-01-14T11:29:23.852-08:00  INFO 84491 --- [           main] i.clustercontroller.MultiClusterManager  : Discovered 1 controllers: [controller-1]

[GeorgeZhai]

maybe as a follow up change.
I think we should abstract the config parsing into a separate class. but doing this field by field as using environment variable is a common pattern

[GeorgeZhai]

maybe as a follow up change.
I think we should abstract the config parsing into a separate class. but doing this field by field as using environment variable is a common pattern