fix(index.d.ts): make Document#id optional so types that use id can use Model<IMyType & Document>

Fix #9684

Author: vkarpov15

index.d.ts

@@ -475,7 +475,7 @@ declare module "mongoose" {
     getChanges(): UpdateQuery<this>;
 
     /** The string version of this documents _id. */
-    id: string;
+    id?: string;
 
     /** Signal that we desire an increment of this documents version. */
     increment(): this;

test/typescript/models.ts

@@ -1,19 +1,37 @@
 import { Schema, Document, Model, connection } from 'mongoose';
 
-interface ITest extends Document {
-  foo: string;
+function conventionalSyntax(): void {
+  interface ITest extends Document {
+    foo: string;
+  }
+  
+  const TestSchema = new Schema({
+    foo: { type: String, required: true },
+  });
+  
+  const Test = connection.model<ITest>('Test', TestSchema);
+  
+  const bar = (SomeModel: Model<ITest>) => console.log(SomeModel);
+  
+  bar(Test);
 }
 
-const TestSchema = new Schema({
-  foo: { type: String, required: true },
-});
+function tAndDocSyntax(): void {
+  interface ITest {
+    id: number;
+    foo: string;
+  }
+  
+  const TestSchema = new Schema({
+    foo: { type: String, required: true },
+  });
 
-const Test = connection.model<ITest>('Test', TestSchema);
+  const Test = connection.model<ITest & Document>('Test', TestSchema);
 
-const bar = (SomeModel: Model<ITest>) => // <<<< error here
-  console.log(SomeModel);
+  const aggregated: Promise<Document> = Test.aggregate([]).then(res => res[0]);
 
-bar(Test);
+  const bar = (SomeModel: Model<ITest & Document>) => console.log(SomeModel);
+}
 
 const ExpiresSchema = new Schema({
   ttl: {
@@ -22,8 +40,6 @@ const ExpiresSchema = new Schema({
   },
 });
 
-const aggregated: Promise<Document> = Test.aggregate([]).then(res => res[0]);
-
 interface IProject extends Document {
   name: String;
 }