update api doc

docs/sources/http_api/dashboard.md

@@ -541,3 +541,97 @@ Content-Length: 97
   "status": "multiple-slugs-exists"
 }
 ```
+
+## Trim input dashboard
+
+`POST /api/dashboards/trim`
+
+Will remove the default values from input dashboard JSON.
+
+**Example Request for trimming dashboard JSON**:
+
+```http
+POST /api/dashboards/uid/trim HTTP/1.1
+Accept: application/json
+Content-Type: application/json
+Authorization: Bearer eyJrIjoiT0tTcG1pUlY2RnVKZTFVaDFsNFZXdE9ZWmNrMkZYbk
+
+{
+    "meta": {
+        "isStarred": false,
+        "url": "/d/cIBgcSjkk/production-overview",
+        "folderId": 2,
+        "folderUid": "l3KqBxCMz",
+        "slug": "production-overview"
+    },
+    "dashboard": {
+        "id": 112,
+        "panels": [
+            {
+                "datasource": null,
+                "description": "",
+                "gridPos": {
+                    "h": 9,
+                    "w": 12,
+                    "x": 0,
+                    "y": 0
+                },
+                "id": 2,
+                "options": {
+                    "feedUrl": "https://grafana.com/blog/news.xml",
+                    "showImage": true
+                },
+                "pluginVersion": "8.1.0-pre",
+                "title": "Panel Title",
+                "type": "news"
+            }
+        ],
+        "title": "test dashboard",
+        "uid": "9lzdzI3Mz",
+        "version": 2
+    }
+}
+```
+
+**Example Response**:
+
+```http
+HTTP/1.1 200
+Content-Type: application/json
+
+{
+    "meta": {
+        "folderId": 2,
+        "folderUid": "l3KqBxCMz",
+        "isStarred": false,
+        "slug": "production-overview",
+        "url": "/d/cIBgcSjkk/production-overview"
+    },
+    "dashboard": {
+        "id": 112,
+        "panels": [
+            {
+                "gridPos": {},
+                "id": 2,
+                "options": {
+                    "feedUrl": "https://grafana.com/blog/news.xml",
+                    "showImage": true
+                },
+                "pluginVersion": "8.1.0-pre",
+                "title": "Panel Title",
+                "type": "news"
+            }
+        ],
+        "title": "test dashboard",
+        "uid": "9lzdzI3Mz",
+        "version": 2
+    }
+}
+```
+
+Status Codes:
+
+- **200** – Trimmed
+- **400** – Errors (invalid json, missing or invalid fields, etc)
+- **401** – Unauthorized
+- **403** – Access denied