Merge branch '7.x'

Author: vkarpov15

test/types/aggregate.test.ts

@@ -152,3 +152,10 @@ function gh13060() {
     }
   }]);
 }
+
+async function gh15300() {
+  const schema = new Schema({ status: String });
+  const TestModel = model('Document', schema);
+
+  await TestModel.aggregate().project('a b -_id');
+}

types/aggregate.d.ts

@@ -124,7 +124,7 @@ declare module 'mongoose' {
     pipeline(): PipelineStage[];
 
     /** Appends a new $project operator to this aggregate pipeline. */
-    project(arg: PipelineStage.Project['$project']): this;
+    project(arg: PipelineStage.Project['$project'] | string): this;
 
     /** Sets the readPreference option for the aggregation query. */
     read(pref: mongodb.ReadPreferenceLike): this;