[v6] Implement Realtime Database (#2195)

* [database] recreate database branch based off of #2185

* [database] cleanup linting issues

* [database] enable tests

* [database] add to tests deps

packages/database/e2e/reference/key.e2e.js

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2016-present Invertase Limited & Contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this library except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+describe('database().ref().key', () => {
+  it('returns null when no reference path is provides', () => {
+    const ref = firebase.database().ref();
+    should.equal(ref.key, null);
+  });
+
+  it('return last token in reference path', () => {
+    const ref1 = firebase.database().ref('foo');
+    const ref2 = firebase.database().ref('foo/bar/baz');
+    ref1.key.should.equal('foo');
+    ref2.key.should.equal('baz');
+  });
+});