Validate System Hook responses against schema

spec/fixtures/api/schemas/public_api/v4/system_hook.json

+{
+  "type": "object",
+  "required": [
+    "id",
+    "url",
+    "created_at",
+    "push_events",
+    "tag_push_events",
+    "merge_requests_events",
+    "repository_update_events",
+    "enable_ssl_verification"
+  ],
+  "properties": {
+    "id": { "type": "integer" },
+    "url": { "type": "string" },
+    "created_at": { "type": "string" },
+    "push_events": { "type": "boolean" },
+    "tag_push_events": { "type": "boolean" },
+    "merge_requests_events": { "type": "boolean" },
+    "repository_update_events": { "type": "boolean" },
+    "enable_ssl_verification": { "type": "boolean" }
+  },
+  "additionalProperties": false
+}

spec/fixtures/api/schemas/public_api/v4/system_hooks.json

+{
+  "type": "array",
+  "items": {
+    "type": "object",
+    "properties" : {
+      "$ref": "./system_hook.json"
+    }
+  }
+}

spec/requests/api/system_hooks_spec.rb

@@ -36,7 +36,7 @@ RSpec.describe API::SystemHooks do
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(response).to include_pagination_headers
-        expect(json_response).to be_an Array
+        expect(response).to match_response_schema('public_api/v4/system_hooks')
         expect(json_response.first).not_to have_key("token")
         expect(json_response.first['url']).to eq(hook.url)
         expect(json_response.first['push_events']).to be false
@@ -70,6 +70,7 @@ RSpec.describe API::SystemHooks do
         get api("/hooks/#{hook.id}", admin)
 
         expect(response).to have_gitlab_http_status(:ok)
+        expect(response).to match_response_schema('public_api/v4/system_hook')
         expect(json_response).to match(
           'id' => be(hook.id),
           'url' => eq(hook.url),
@@ -121,6 +122,7 @@ RSpec.describe API::SystemHooks do
       post api('/hooks', admin), params: { url: 'http://mep.mep' }
 
       expect(response).to have_gitlab_http_status(:created)
+      expect(response).to match_response_schema('public_api/v4/system_hook')
       expect(json_response['enable_ssl_verification']).to be true
       expect(json_response['push_events']).to be false
       expect(json_response['tag_push_events']).to be false
@@ -142,6 +144,7 @@ RSpec.describe API::SystemHooks do
         }
 
       expect(response).to have_gitlab_http_status(:created)
+      expect(response).to match_response_schema('public_api/v4/system_hook')
       expect(json_response['enable_ssl_verification']).to be false
       expect(json_response['push_events']).to be true
       expect(json_response['tag_push_events']).to be true