feat: Add an API to support querying metrics by ChannelType (#13255)

This API gives you how many conversations exist per channel, broken down
by status in a given time period. The max time period is capped to 6
months for now.

**Input Params:**
- **since:** Unix timestamp (seconds) - start of date range
- **until:** Unix timestamp (seconds) - end of date range


**Response Payload:**

```json
{
  "Channel::Sms": {
    "resolved": 85,
    "snoozed": 10,
    "open": 5,
    "pending": 5,
    "total": 100
  },
  "Channel::Email": {
    "resolved": 72,
    "snoozed": 15,
    "open": 13,
    "pending": 13,
    "total": 100
  },
  "Channel::WebWidget": {
    "resolved": 90,
    "snoozed": 7,
    "open": 3,
    "pending": 3,
    "total": 100
  }
}
```

**Definitons:**
resolved = Number of conversations created within the selected time
period that are currently marked as resolved.
snoozed = Number of conversations created within the selected time
period that are currently marked as snoozed.
pending = Number of conversations created within the selected time
period that are currently marked as pending.
open = Number of conversations created within the selected time period
that are currently open.
total = Total number of conversations created within the selected time
period, across all statuses.

swagger/paths/application/reports/channel_summary.yml

@@ -0,0 +1,30 @@
+tags:
+  - Reports
+operationId: get-channel-summary-report
+summary: Get conversation statistics grouped by channel type
+security:
+  - userApiKey: []
+description: |
+  Get conversation counts grouped by channel type and status for a given date range.
+  Returns statistics for each channel type including open, resolved, pending, snoozed, and total conversation counts.
+
+  **Note:** This API endpoint is available only in Chatwoot version 4.10.0 and above. The date range is limited to a maximum of 6 months.
+responses:
+  '200':
+    description: Success
+    content:
+      application/json:
+        schema:
+          $ref: '#/components/schemas/channel_summary'
+  '400':
+    description: Date range exceeds 6 months limit
+    content:
+      application/json:
+        schema:
+          $ref: '#/components/schemas/bad_request_error'
+  '403':
+    description: Access denied
+    content:
+      application/json:
+        schema:
+          $ref: '#/components/schemas/bad_request_error'