doc(api-test): add multi-stage demo for api-test 2.0 (#47)

actions/api-test/2.0/README.md

@@ -4,24 +4,41 @@
 
 #### 使用
 
+推荐通过图形化界面进行编辑。
+
+通过声明出参，可以将接口返回的数据传递给下游 action，例如下例中的 `a-cookie`。
+
 ```yaml
-api-test:
-  version: 2.0
-  params:
-    name: 访问 Dice 官网
-    url: https://dice.terminus.io
-    method: GET
-    params:
-      - key: p1
-        value: v1
-      - key: p2
-        value: v2
-    headers:
-      - key: h1
-        value: v1
-      - key: h2
-        value: v2
-    body:
-      type: application/json
-      content: '{"name":"dice"}'
-```
+version: "1.1"
+stages:
+  - stage:
+      - api-test:
+          description: 执行单个接口测试。上层可以通过 pipeline.yml 编排一组接口测试的执行顺序。
+          version: "2.0"
+          params:
+            asserts:
+              - arg: a-cookie
+                operator: not_empty
+            body:
+              type: none
+            method: GET
+            out_params:
+              - expression: Set-Cookie
+                key: a-cookie
+                source: header
+            url: https://www.erda.cloud/api/users/me
+          timeout: 3600
+  - stage:
+      - custom-script:
+          alias: cookie-printer
+          description: 运行自定义命令
+          version: "2.0"
+          commands:
+            - |-
+              c="${{ outputs.api-test.a-cookie }}"
+              echo "I got a cookie: $c"
+            - 'echo "action meta: b-cookie=$c"'
+          resources:
+            cpu: 0.1
+            mem: 256
+```