UpdateType(mongoose): add interfaces for promisified schema validators

Add `AsyncPromiseValidationFn`, `AsyncPromiseValidationOpts` as described in this document https://mongoosejs.com/docs/validation.html

types/mongoose/index.d.ts

@@ -977,7 +977,9 @@ declare module "mongoose" {
     validate?: RegExp | [RegExp, string] |
       SchemaTypeOpts.ValidateFn<T> | [SchemaTypeOpts.ValidateFn<T>, string] |
       SchemaTypeOpts.ValidateOpts | SchemaTypeOpts.ValidateOpts[] |
-      SchemaTypeOpts.AsyncValidateOpts | SchemaTypeOpts.AsyncValidateOpts[];
+      SchemaTypeOpts.AsyncValidateOpts | SchemaTypeOpts.AsyncValidateOpts[] |
+      SchemaTypeOpts.AsyncPromiseValidationFn<T> | SchemaTypeOpts.AsyncPromiseValidationFn<T>[] |
+      SchemaTypeOpts.AsyncPromiseValidationOpts | SchemaTypeOpts.AsyncPromiseValidationOpts[];
 
     /** Declares an unique index. */
     unique?: boolean | any;
@@ -1060,6 +1062,14 @@ declare module "mongoose" {
       validator: AsyncValidateFn<any>;
     }
 
+    interface AsyncPromiseValidationFn<T> {
+      (value: T): Promise<boolean>;
+    }
+
+    interface AsyncPromiseValidationOpts extends ValidateOptsBase {
+      validator: AsyncPromiseValidationFn<any>;
+    }
+
     interface EnumOpts<T> {
       values?: T[];
       message?: string;

types/mongoose/mongoose-tests.ts

@@ -524,7 +524,15 @@ new mongoose.Schema({
         setImmediate(done, true);
       }
     }
-  }
+  },
+  promiseValidated: {
+    type: Number,
+    validate: {
+      validator: async (val: number) => {
+        return val === 2;
+      }
+    }
+  },
 });
 new mongoose.Schema({ name: { type: String, validate: [
   { validator: () => {return true}, msg: 'uh oh' },