Throw error when model relation name is trigger

Defining a model relation with the name "trigger" causes the model not
able to insert records. No error is thrown when a model relation with
the name "trigger" is defined. Adding a check for the model relation
name "trigger" will now throw an error.

lib/registry.js

@@ -118,6 +118,12 @@ Registry.prototype.createModel = function(name, properties, options) {
     }
   }
 
+  var invalidRelationName = checkRelationName(options);
+
+  if (invalidRelationName.length > 0) {
+    throw new Error(g.f('Invalid relation name `%s` for model `%s`.', invalidRelationName,  name));
+  }
+
   BaseModel = BaseModel || this.getModel('PersistedModel');
   var model = BaseModel.extend(name, properties, options);
   model.registry = this;
@@ -146,6 +152,30 @@ function buildModelOptionsFromConfig(config) {
   return options;
 }
 
+/*
+ * Check the name of a model relation name against a list of reserved names.
+ * @param {Object[]} options
+ * @return {string} The name of the reserved relation name.
+ */
+function checkRelationName(options) {
+  var reservedNames = ['trigger'];
+  var invalidRelationName = '';
+
+  if (options.hasOwnProperty('relations')) {
+    Object.keys(options['relations']).forEach(function(relationName) {
+      var isReserved = reservedNames.some(function(reservedName) {
+        return relationName === reservedName;
+      });
+
+      if (isReserved) {
+        invalidRelationName = relationName;
+      }
+    });
+  }
+
+  return invalidRelationName;
+}
+
 /*
  * Add the acl entry to the acls
  * @param {Object[]} acls

test/registries.test.js

@@ -17,6 +17,27 @@ describe('Registry', function() {
       expect(function() { app.registry.createModel('aModel', props, opts); })
         .to.throw(/model\s`aModel`(.*)unknown\smodel\s`nonexistent`/);
     });
+
+    it('should throw error upon reserved relation name `trigger`', function() {
+      var app = loopback();
+      var fooModel = {
+        name: 'Foo',
+        properties: {
+          name: 'string',
+        },
+        options: {
+          relations: {
+            trigger: {
+              model: 'Bar',
+              type: 'hasMany',
+            },
+          },
+        },
+      };
+
+      expect(function() { app.registry.createModel(fooModel); })
+        .to.throw('Invalid relation name `trigger` for model `Foo`.');
+    });
   });
 
   describe('one per app', function() {