feat: backport findModel to v6 (#16705)

Co-authored-by: Carlos Bardasano <cbardasano@alaudaingenieria.es>
Co-authored-by: Rik Smale <13023439+WikiRik@users.noreply.github.com>

src/model-manager.d.ts

@@ -10,6 +10,7 @@ export class ModelManager {
   public addModel<T extends ModelType>(model: T): T;
   public removeModel(model: ModelType): void;
   public getModel(against: unknown, options?: { attribute?: string }): typeof Model;
+  public findModel(callback: (model: typeof Model) => boolean): typeof Model | undefined
 
   /**
    * Returns an array that lists every model, sorted in order

src/model-manager.js

@@ -30,6 +30,10 @@ class ModelManager {
     return this.models.find(model => model[options.attribute] === against);
   }
 
+  findModel(callback) {
+    return this.models.find(callback);
+  }
+
   get all() {
     return this.models;
   }

test/integration/sequelize.test.js

@@ -230,6 +230,17 @@ describe(Support.getTestDialectTeaser('Sequelize'), () => {
     });
   });
 
+  describe('modelManager', () => {
+    it('allows to find a model using a callback', function() {
+      const project = this.sequelize.define('Project', {
+        name: DataTypes.STRING
+      });
+
+      const model = this.sequelize.modelManager.findModel(m => m.name.toLowerCase() === 'project');
+      expect(model).to.equal(project);
+    });
+  });
+
   describe('set', () => {
     it('should be configurable with global functions', function() {
       const defaultSetterMethod = sinon.spy(),