Add API documentation for inbox, agent, and team summary report (#13409)

- Add API documentation for inbox, agent, and team summary report
endpoints
- These endpoints return conversation statistics grouped by
inbox/agent/team for a given date range

Endpoints documented:
GET /api/v2/accounts/{account_id}/summary_reports/inbox │ Conversation
stats grouped by inbox │
GET /api/v2/accounts/{account_id}/summary_reports/agent │ Conversation
stats grouped by agent │
GET /api/v2/accounts/{account_id}/summary_reports/team │ Conversation
stats grouped by team │

Query parameters (all endpoints):
- since - Start timestamp (Unix)
- until - End timestamp (Unix)
- business_hours - Calculate metrics using business hours only

Response fields:
- id - Inbox/Agent/Team ID
- conversations_count - Total conversations in date range
- resolved_conversations_count - Resolved conversations in date range
- avg_resolution_time - Average resolution time (seconds)
- avg_first_response_time - Average first response time (seconds)
- avg_reply_time - Average reply time (seconds)

swagger/definitions/resource/reports/inbox_summary.yml

@@ -0,0 +1,39 @@
+type: array
+description: Inbox summary report containing conversation statistics grouped by inbox.
+items:
+  type: object
+  properties:
+    id:
+      type: number
+      description: The inbox ID
+    conversations_count:
+      type: number
+      description: Number of conversations created in the inbox during the date range
+    resolved_conversations_count:
+      type: number
+      description: Number of conversations resolved in the inbox during the date range
+    avg_resolution_time:
+      type: number
+      nullable: true
+      description: Average time (in seconds) to resolve conversations. Null if no data available.
+    avg_first_response_time:
+      type: number
+      nullable: true
+      description: Average time (in seconds) for the first response. Null if no data available.
+    avg_reply_time:
+      type: number
+      nullable: true
+      description: Average time (in seconds) between replies. Null if no data available.
+example:
+  - id: 1
+    conversations_count: 150
+    resolved_conversations_count: 120
+    avg_resolution_time: 3600
+    avg_first_response_time: 300
+    avg_reply_time: 600
+  - id: 2
+    conversations_count: 75
+    resolved_conversations_count: 60
+    avg_resolution_time: 1800
+    avg_first_response_time: 180
+    avg_reply_time: 420