feat: Document subscriptions (#3834)

Co-authored-by: Tom Moor <tom.moor@gmail.com>

server/models/Subscription.ts

@@ -0,0 +1,46 @@
+import {
+  Column,
+  DataType,
+  BelongsTo,
+  ForeignKey,
+  Table,
+  IsIn,
+  Scopes,
+} from "sequelize-typescript";
+import Document from "./Document";
+import User from "./User";
+import ParanoidModel from "./base/ParanoidModel";
+import Fix from "./decorators/Fix";
+
+@Scopes(() => ({
+  withUser: {
+    include: [
+      {
+        association: "user",
+      },
+    ],
+  },
+}))
+@Table({ tableName: "subscriptions", modelName: "subscription" })
+@Fix
+class Subscription extends ParanoidModel {
+  @BelongsTo(() => User, "userId")
+  user: User;
+
+  @ForeignKey(() => User)
+  @Column(DataType.UUID)
+  userId: string;
+
+  @BelongsTo(() => Document, "documentId")
+  document: Document | null;
+
+  @ForeignKey(() => Document)
+  @Column(DataType.UUID)
+  documentId: string | null;
+
+  @IsIn([["documents.update"]])
+  @Column(DataType.STRING)
+  event: string;
+}
+
+export default Subscription;