Expose notify platform targets as individual services (#2837)

* First pass on providing individual services for all possible targets that a notification platform supports.

* Add a quite hacky first version of notification groups

* Add a docstring for get_targets

* Register group service under notifygroup/ and safely check for notifygroups in config

* Remove notifygroups, because it belongs in its own PR

* Make @balloob requested changes

* get_targets()->targets

* Add tests for notify targets exposed as individual services

* If we dont have a platform name set in configuration, lets use the name of the platform instead of notify

* Fix test docstring.

* Dont use a dictionary for just one value

* No need to double slugify

* targets is now just a list of strings instead of a dict

tests/components/notify/test_demo.py

@@ -22,6 +22,7 @@ class TestNotifyDemo(unittest.TestCase):
             }
         }))
         self.events = []
+        self.calls = []
 
         def record_event(event):
             """Record event to send notification."""
@@ -33,6 +34,10 @@ class TestNotifyDemo(unittest.TestCase):
         """"Stop down everything that was started."""
         self.hass.stop()
 
+    def record_calls(self, *args):
+        """Helper for recording calls."""
+        self.calls.append(args)
+
     def test_sending_none_message(self):
         """Test send with None as message."""
         notify.send_message(self.hass, None)
@@ -93,3 +98,29 @@ data_template:
                     'sound':
                     'US-EN-Morgan-Freeman-Roommate-Is-Arriving.wav'}}
         } == self.events[0].data
+
+    def test_targets_are_services(self):
+        """Test that all targets are exposed as individual services."""
+        self.assertIsNotNone(self.hass.services.has_service("notify", "demo"))
+        service = "demo_test_target"
+        self.assertIsNotNone(self.hass.services.has_service("notify", service))
+
+    def test_messages_to_targets_route(self):
+        """Test message routing to specific target services."""
+        self.hass.bus.listen_once("notify", self.record_calls)
+
+        self.hass.services.call("notify", "demo_test_target",
+                                {'message': 'my message',
+                                 'title': 'my title',
+                                 'data': {'hello': 'world'}})
+
+        self.hass.pool.block_till_done()
+
+        data = self.calls[0][0].data
+
+        assert {
+            'message': 'my message',
+            'target': 'test target',
+            'title': 'my title',
+            'data': {'hello': 'world'}
+        } == data