actions: retrieve dashboard URL

Allow sunbeam to retrieve the public ingress URL for the
dashboard to avoid the user having to use juju commands
to interrogate the model directly.

Change-Id: Ia35f66ecfd282c70f329d955413fa26f464a08a2

charms/horizon-k8s/actions.yaml

@@ -1,2 +1,2 @@
-# NOTE: no actions yet!
+get-dashboard-url:
-{ }
+  description: URL for access to the Horizon OpenStack Dashboard.

charms/horizon-k8s/src/charm.py

@@ -84,6 +84,17 @@ class OpenstackDashboardOperatorCharm(sunbeam_charm.OSBaseOperatorAPICharm):
         "identity-credentials",
     }
 
+    def __init__(self, framework):
+        super().__init__(framework)
+        self.framework.observe(
+            self.on.get_dashboard_url_action,
+            self._get_dashboard_url_action,
+        )
+
+    def _get_dashboard_url_action(self, event):
+        """Retrieve the URL for the Horizon OpenStack Dashboard."""
+        event.set_results({"url": self.public_url})
+
     @property
     def default_public_ingress_port(self):
         """Default public ingress port."""

charms/horizon-k8s/tests/actions.yaml

@@ -0,0 +1 @@
+../actions.yaml

charms/horizon-k8s/tests/unit/test_dashboard_charm.py

@@ -110,3 +110,11 @@ class TestDashboardOperatorCharm(test_utils.CharmTestCase):
         self.check_file(
             "openstack-dashboard", "/etc/openstack-dashboard/local_settings.py"
         )
+
+    def test_get_dashboard_url_action(self):
+        """Test admin account action."""
+        action_event = mock.MagicMock()
+        self.harness.charm._get_dashboard_url_action(action_event)
+        action_event.set_results.assert_called_with(
+            {"url": "http://dashboard.juju:80"}
+        )