Disabled changing webhook's integration_id through PUT API

refs #12033

- Allowing to change parent integration opens up possible security holes and has no clear usecase at the moment. After a webhook record is created it should not be possible to change parent integration.
- Had do partially duplicate JSON schema definition from webhooks definition as there is no proper composition technique available in current version of JSON Schema.

core/server/api/canary/utils/validators/input/schemas/webhooks-edit.json

@@ -10,7 +10,64 @@
             "type": "array",
             "minItems": 1,
             "maxItems": 1,
-            "items": {"$ref": "webhooks#/definitions/webhook"}
+            "items": {
+                "type": "object",
+                "additionalProperties": false,
+                "properties": {
+                    "event": {
+                        "type": "string",
+                        "maxLength": 50,
+                        "isLowercase": true
+                    },
+                    "target_url": {
+                        "type": "string",
+                        "format": "uri-reference",
+                        "maxLength": 2000
+                    },
+                    "name": {
+                        "type": ["string", "null"],
+                        "maxLength": 191
+                    },
+                    "secret": {
+                        "type": ["string", "null"],
+                        "maxLength": 191
+                    },
+                    "api_version": {
+                        "type": ["string", "null"],
+                        "maxLength": 50
+                    },
+                    "integration_id": {
+                        "strip": true
+                    },
+                    "id": {
+                        "strip": true
+                    },
+                    "status": {
+                        "strip": true
+                    },
+                    "last_triggered_at": {
+                        "strip": true
+                    },
+                    "last_triggered_status": {
+                        "strip": true
+                    },
+                    "last_triggered_error": {
+                        "strip": true
+                    },
+                    "created_at": {
+                        "strip": true
+                    },
+                    "created_by": {
+                        "strip": true
+                    },
+                    "updated_at": {
+                        "strip": true
+                    },
+                    "updated_by": {
+                        "strip": true
+                    }
+                }
+            }
         }
     },
     "required": ["webhooks"]

test/api-acceptance/admin/webhooks_spec.js

@@ -99,7 +99,8 @@ describe('Webhooks API', function () {
                         webhooks: [{
                             name: 'Edit Test',
                             event: 'subscriber.added',
-                            target_url: 'https://example.com/new-subscriber'
+                            target_url: 'https://example.com/new-subscriber',
+                            integration_id: 'ignore_me'
                         }]
                     })
                     .expect(200)