Implement new create and manager trigger UI

Implements the new trigger setup user interface, which is now a linear workflow found on its own page, rather than a tiny modal dialog

Fixes #1187

buildtrigger/basehandler.py

@@ -1,7 +1,10 @@
+from abc import ABCMeta, abstractmethod
+from jsonschema import validate
+from six import add_metaclass
+
 from endpoints.building import PreparedBuild
 from data import model
 from buildtrigger.triggerutil import get_trigger_config, InvalidServiceException
-from jsonschema import validate
 
 METADATA_SCHEMA = {
   'type': 'object',
@@ -18,7 +21,7 @@ METADATA_SCHEMA = {
     'ref': {
       'type': 'string',
       'description': 'git reference for a git commit',
-      'pattern': '^refs\/(heads|tags|remotes)\/(.+)$',
+      'pattern': r'^refs\/(heads|tags|remotes)\/(.+)$',
     },
     'default_branch': {
       'type': 'string',
@@ -86,6 +89,7 @@ METADATA_SCHEMA = {
 }
 
 
+@add_metaclass(ABCMeta)
 class BuildTriggerHandler(object):
   def __init__(self, trigger, override_config=None):
     self.trigger = trigger
@@ -96,72 +100,90 @@ class BuildTriggerHandler(object):
     """ Returns the auth token for the trigger. """
     return self.trigger.auth_token
 
+  @abstractmethod
   def load_dockerfile_contents(self):
     """
     Loads the Dockerfile found for the trigger's config and returns them or None if none could
     be found/loaded.
     """
-    raise NotImplementedError
+    pass
 
-  def list_build_sources(self):
+  @abstractmethod
+  def list_build_source_namespaces(self):
     """
     Take the auth information for the specific trigger type and load the
-    list of build sources(repositories).
+    list of namespaces that can contain build sources.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
+  def list_build_sources_for_namespace(self, namespace):
+    """
+    Take the auth information for the specific trigger type and load the
+    list of repositories under the given namespace.
+    """
+    pass
+
+  @abstractmethod
   def list_build_subdirs(self):
     """
     Take the auth information and the specified config so far and list all of
     the possible subdirs containing dockerfiles.
     """
-    raise NotImplementedError
+    pass
 
-  def handle_trigger_request(self):
+  @abstractmethod
+  def handle_trigger_request(self, request):
     """
     Transform the incoming request data into a set of actions. Returns a PreparedBuild.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def is_active(self):
     """
     Returns True if the current build trigger is active. Inactive means further
     setup is needed.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def activate(self, standard_webhook_url):
     """
     Activates the trigger for the service, with the given new configuration.
     Returns new public and private config that should be stored if successful.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def deactivate(self):
     """
     Deactivates the trigger for the service, removing any hooks installed in
     the remote service. Returns the new config that should be stored if this
     trigger is going to be re-activated.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def manual_start(self, run_parameters=None):
     """
     Manually creates a repository build for this trigger. Returns a PreparedBuild.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def list_field_values(self, field_name, limit=None):
     """
     Lists all values for the given custom trigger field. For example, a trigger might have a
     field named "branches", and this method would return all branches.
     """
-    raise NotImplementedError
+    pass
 
+  @abstractmethod
   def get_repository_url(self):
     """ Returns the URL of the current trigger's repository. Note that this operation
         can be called in a loop, so it should be as fast as possible. """
-    raise NotImplementedError
+    pass
 
   @classmethod
   def service_name(cls):