feat: validate OpenAPI spec using Skooma (#13623)

Adds Skooma-based OpenAPI validation so SDK-facing request specs can
assert that documented request and response contracts match real Rails
behavior. This also upgrades the spec to OpenAPI 3.1 and fixes contract
drift uncovered while validating core application and platform
resources.

Closes
None

Why
We want CI to catch OpenAPI drift before it reaches SDK consumers. While
wiring validation in, this PR surfaced several mismatches between the
documented contract and what the Rails endpoints actually accept or
return.

What this change does
- Adds Skooma-backed OpenAPI validation to the request spec flow and a
dedicated OpenAPI validation spec.
- Migrates nullable schema definitions to OpenAPI 3.1-compatible unions.
- Updates core SDK-facing schemas and payloads across accounts,
contacts, conversations, inboxes, messages, teams, reporting events, and
platform account resources.
- Documents concrete runtime cases that were previously missing or
inaccurate, including nested `profile` update payloads, multipart avatar
uploads, required profile update bodies, nullable inbox feature flags,
and message sender types that include both `Captain::Assistant` and
senderless activity-style messages.
- Regenerates the committed Swagger JSON and tag-group artifacts used by
CI sync checks.

Validation
- `bundle exec rake swagger:build`
- `bundle exec rspec spec/swagger/openapi_spec.rb`

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

swagger/definitions/resource/message.yml

@@ -17,37 +17,49 @@ properties:
     description: The ID of the conversation
   message_type:
     type: integer
-    enum: [0, 1, 2]
+    enum: [0, 1, 2, 3]
     description: The type of the message
   created_at:
     type: integer
     description: The time at which message was created
   updated_at:
-    type: integer
+    type:
+      - integer
+      - string
     description: The time at which message was updated
   private:
     type: boolean
     description: The flags which shows whether the message is private or not
   status:
-    type: string
-    enum: ["sent", "delivered", "read", "failed"]
+    type:
+      - string
+      - 'null'
+    enum: ["sent", "delivered", "read", "failed", null]
     description: The status of the message
   source_id:
-    type: string
+    type:
+      - string
+      - 'null'
     description: The source ID of the message
   content_type:
-    type: string
-    enum: ["text", "input_select", "cards", "form"]
+    type:
+      - string
+      - 'null'
+    enum: ["text", "input_text", "input_textarea", "input_email", "input_select", "cards", "form", "article", "incoming_email", "input_csat", "integrations", "sticker", "voice_call", null]
     description: The type of the template message
   content_attributes:
     type: object
     description: The content attributes for each content_type
   sender_type:
-    type: string
-    enum: ["contact", "agent", "agent_bot"]
+    type:
+      - string
+      - 'null'
+    enum: ["Contact", "User", "AgentBot", "Captain::Assistant", null]
     description: The type of the sender
   sender_id:
-    type: number
+    type:
+      - number
+      - 'null'
     description: The ID of the sender
   external_source_ids:
     type: object
@@ -56,16 +68,24 @@ properties:
     type: object
     description: The additional attributes of the message
   processed_message_content:
-    type: string
+    type:
+      - string
+      - 'null'
     description: The processed message content
   sentiment:
-    type: object
+    type:
+      - object
+      - 'null'
     description: The sentiment of the message
   conversation:
-    type: object
+    type:
+      - object
+      - 'null'
     description: The conversation object
   attachment:
-    type: object
+    type:
+      - object
+      - 'null'
     description: The file object attached to the image
   sender:
     type: object