feat: Update swagger to openapi 3.0.4, update request payloads with examples (#11533)

# Pull Request Template

## Description

Updates the public swagger spec to be OpenAPI 3.0.4 compliant. Regarding
#7893, I'm investigating the use of
[oas_rails](https://github.com/a-chacon/oas_rails) to auto-generate the
documentation along with correct expected payloads.
Mostly fixes #10531, related to #7893

## Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality not to work as expected)
- [ ] This change requires a documentation update

## How Has This Been Tested?

Copied spec into swagger editor, reviewed outputs:

![openapi](https://github.com/user-attachments/assets/bd43f895-74bb-4373-ba6d-c5b190b699dd)

Note that this shows two errors with the `DELETE` endpoints as
technically these should not have a `requestBody` - in which case we
should be making use of another HTTP verb or another endpoint.

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Daniel Jimenez <devildan.knex@gmail.com>
Co-authored-by: Daniel Jimenez <daniel.jimenez@spark64.com>

swagger/definitions/resource/contact_conversation_message.yml

@@ -0,0 +1,109 @@
+type: object
+properties:
+  id:
+    type: integer
+    description: ID of the message
+  content:
+    type: string
+    description: Content of the message
+  account_id:
+    type: integer
+    description: ID of the account
+  inbox_id:
+    type: integer
+    description: ID of the inbox
+  conversation_id:
+    type: integer
+    description: ID of the conversation
+  message_type:
+    type: integer
+    description: Type of the message
+  created_at:
+    type: integer
+    description: Timestamp when message was created
+  updated_at:
+    type: string
+    description: Formatted datetime when message was updated
+  private:
+    type: boolean
+    description: Whether the message is private
+  status:
+    type: string
+    description: Status of the message
+  source_id:
+    type: string
+    description: Source ID of the message
+    nullable: true
+  content_type:
+    type: string
+    description: Type of the content
+  content_attributes:
+    type: object
+    description: Attributes of the content
+  sender_type:
+    type: string
+    description: Type of the sender
+    nullable: true
+  sender_id:
+    type: integer
+    description: ID of the sender
+    nullable: true
+  external_source_ids:
+    type: object
+    description: External source IDs
+  additional_attributes:
+    type: object
+    description: Additional attributes of the message
+  processed_message_content:
+    type: string
+    description: Processed message content
+    nullable: true
+  sentiment:
+    type: object
+    description: Sentiment analysis of the message
+  conversation:
+    type: object
+    description: Conversation details
+    properties:
+      assignee_id:
+        type: integer
+        description: ID of the assignee
+        nullable: true
+      unread_count:
+        type: integer
+        description: Count of unread messages
+      last_activity_at:
+        type: integer
+        description: Timestamp of last activity
+      contact_inbox:
+        type: object
+        description: Contact inbox details
+        properties:
+          source_id:
+            type: string
+            description: Source ID of the contact inbox
+  sender:
+    type: object
+    description: Details of the sender
+    properties:
+      id:
+        type: integer
+        description: ID of the sender
+      name:
+        type: string
+        description: Name of the sender
+      available_name:
+        type: string
+        description: Available name of the sender
+      avatar_url:
+        type: string
+        description: URL of the sender's avatar
+      type:
+        type: string
+        description: Type of the sender
+      availability_status:
+        type: string
+        description: Availability status of the sender
+      thumbnail:
+        type: string
+        description: Thumbnail URL of the sender