Clarify migration semantics and harden v9 additive-schema guardrails

[Copilot]

The issue asked what migrations actually do in this repository and whether v9 is modifying existing schema vs creating new schema. This PR makes migration behavior explicit in docs and tightens the v9 migration assertions to reflect additive-only intent.

• Migration behavior documentation

  • Added a focused README section describing startup migration flow:
    • version detection via schema_version
    • ordered transactional execution of newer migrations
    • optional Rust backfill execution before commit
  • Documented migration categories (schema_setup, migration, migration_backfill) and current mapping (v0-v6 setup-only, v7-v9 upgrade-capable).

• v9 migration intent made explicit

  • Clarified that v9 is additive and limited to creating the gateways table + indexes (no alter/drop of existing tables).

• v9 test strengthened

  • Updated v9_schema_is_additive_only to:
    • assert expected table/index creation statements
    • assert absence of destructive/shape-changing statements
    • use case-insensitive matching for resilience.

assert!(migration.contains("create table gateways"));
assert!(migration.contains("create index if not exists gateways_federation_id"));
assert!(migration.contains("create index if not exists gateways_node_pub_key"));
assert!(!migration.contains("alter table"));
assert!(!migration.contains("drop table"));

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Latest commit: c60d04f

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Project	Deployment	Actions	Updated (UTC)
fedimint-observer	Ready	Preview, Comment	Mar 24, 2026 10:44am