Document merchants API endpoints (#980)

Add rswag request specs for merchants index/show and define a MerchantDetail schema used by the docs. Update the generated OpenAPI document with merchants paths and schema.

docs/api/openapi.yaml

@@ -357,6 +357,31 @@ components:
           format: uuid
         name:
           type: string
+    MerchantDetail:
+      type: object
+      required:
+      - id
+      - name
+      - type
+      - created_at
+      - updated_at
+      properties:
+        id:
+          type: string
+          format: uuid
+        name:
+          type: string
+        type:
+          type: string
+          enum:
+          - FamilyMerchant
+          - ProviderMerchant
+        created_at:
+          type: string
+          format: date-time
+        updated_at:
+          type: string
+          format: date-time
     Tag:
       type: object
       required:
@@ -848,6 +873,49 @@ components:
         pagination:
           "$ref": "#/components/schemas/Pagination"
 paths:
+  "/api/v1/merchants":
+    get:
+      summary: List merchants
+      tags:
+      - Merchants
+      security:
+      - apiKeyAuth: []
+      responses:
+        '200':
+          description: merchants listed
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  "$ref": "#/components/schemas/MerchantDetail"
+  "/api/v1/merchants/{id}":
+    parameters:
+    - name: id
+      in: path
+      required: true
+      description: Merchant ID
+      schema:
+        type: string
+    get:
+      summary: Retrieve a merchant
+      tags:
+      - Merchants
+      security:
+      - apiKeyAuth: []
+      responses:
+        '200':
+          description: merchant retrieved
+          content:
+            application/json:
+              schema:
+                "$ref": "#/components/schemas/MerchantDetail"
+        '404':
+          description: merchant not found
+          content:
+            application/json:
+              schema:
+                "$ref": "#/components/schemas/ErrorResponse"
   "/api/v1/accounts":
     get:
       summary: List accounts