feat: remove a Model from all registries

Add API allowing consumers (e.g. LoopBack) to remove a Model from all
juggler registries:
 - ModelBuilder's models
 - ModelBuilder's definitions
 - Connector registry of models

lib/datasource.js

@@ -800,6 +800,16 @@ DataSource.prototype.define = function defineClass(className, properties, settin
   return modelClass;
 };
 
+/**
+ * Remove a model from the registry.
+ *
+ * @param {String} modelName
+ */
+DataSource.prototype.deleteModelByName = function(modelName) {
+  this.modelBuilder.deleteModelByName(modelName);
+  delete this.connector._models[modelName];
+};
+
 /**
  * Mixin DataAccessObject methods.
  *

lib/model-builder.js

@@ -806,6 +806,16 @@ ModelBuilder.prototype.copyModel = function copyModel(Master) {
   return Slave;
 };
 
+/**
+ * Remove a model from the registry.
+ *
+ * @param {String} modelName
+ */
+ModelBuilder.prototype.deleteModelByName = function(modelName) {
+  delete this.models[modelName];
+  delete this.definitions[modelName];
+};
+
 /*!
  * Define hidden property
  */

test/datasource.test.js

@@ -154,4 +154,36 @@ describe('DataSource', function() {
     dataSource.name.should.equal('myDataSource');
     dataSource.connector.should.equal(mockConnector);
   });
+
+  describe('deleteModelByName()', () => {
+    it('removes the model from ModelBuilder registry', () => {
+      const ds = new DataSource('ds', {connector: 'memory'});
+
+      ds.createModel('TestModel');
+      Object.keys(ds.modelBuilder.models)
+        .should.containEql('TestModel');
+      Object.keys(ds.modelBuilder.definitions)
+        .should.containEql('TestModel');
+
+      ds.deleteModelByName('TestModel');
+
+      Object.keys(ds.modelBuilder.models)
+        .should.not.containEql('TestModel');
+      Object.keys(ds.modelBuilder.definitions)
+        .should.not.containEql('TestModel');
+    });
+
+    it('removes the model from connector registry', () => {
+      const ds = new DataSource('ds', {connector: 'memory'});
+
+      ds.createModel('TestModel');
+      Object.keys(ds.connector._models)
+        .should.containEql('TestModel');
+
+      ds.deleteModelByName('TestModel');
+
+      Object.keys(ds.connector._models)
+        .should.not.containEql('TestModel');
+    });
+  });
 });