Support broadcast messages

shared/models/server/custom-config.model.ts

@@ -1,4 +1,5 @@
 import { NSFWPolicyType } from '../videos/nsfw-policy.type'
+import { BroadcastMessageLevel } from './broadcast-message-level.type'
 
 export interface CustomConfig {
   instance: {
@@ -131,4 +132,11 @@ export interface CustomConfig {
       }
     }
   }
+
+  broadcastMessage: {
+    enabled: boolean
+    message: string
+    level: BroadcastMessageLevel
+    dismissable: boolean
+  }
 }