Emit deprecation warning for federated domain/project APIs

Before the identity API documentation lived in-tree, it lived in the
openstack/keystone-specs project. Before that it lived in it's own
identity-api repository. A long time ago we merged a patch [0] to that
project to deprecate the project and domain APIs in the federation
path. That documentation has since been copied and migrated to the
keystone-specs repository and now keystone itself.

Even though we've deprecated those API in the documentation, we never
formally deprecated them in code using ``versionutils``. This commit
does that. Now a message will be logged anytime that API is used
instead of GET /auth/domains or GET /auth/projects. This makes the
implementation of keystone consistent with documentation we merged
ages ago.

[0] If0c010119512d6a159ce82147a87c4698205a648

Change-Id: I88cb587c7cd69fef400b2eaf7dffda655355b710

keystone/federation/controllers.py

@@ -15,6 +15,7 @@
 import string
 
 from oslo_log import log
+from oslo_log import versionutils
 from six.moves import http_client
 from six.moves import urllib
 import webob
@@ -439,6 +440,10 @@ class DomainV3(controller.V3Controller):
         super(DomainV3, self).__init__()
         self.get_member_from_driver = self.resource_api.get_domain
 
+    @versionutils.deprecated(
+        as_of=versionutils.deprecated.JUNO,
+        in_favor_of='GET /v3/auth/domains/',
+    )
     @controller.protected()
     def list_domains_for_user(self, request):
         """List all domains available to an authenticated user.
@@ -465,6 +470,10 @@ class ProjectAssignmentV3(controller.V3Controller):
         super(ProjectAssignmentV3, self).__init__()
         self.get_member_from_driver = self.resource_api.get_project
 
+    @versionutils.deprecated(
+        as_of=versionutils.deprecated.JUNO,
+        in_favor_of='GET /v3/auth/projects/',
+    )
     @controller.protected()
     def list_projects_for_user(self, request):
         """List all projects available to an authenticated user.

releasenotes/notes/deprecated-as-of-queens-8ad7f826e4f08f57.yaml

@@ -0,0 +1,9 @@
+---
+deprecations:
+  - |
+    The ``/OS-FEDERATION/projects`` and ``/OS-FEDERATION/domains`` APIs are
+    deprecated in favor of the ``/v3/auth/projects`` and ``/v3/auth/domains``
+    APIs. These APIs were originally marked as deprecated during the Juno
+    release cycle, but we never deprecated using ``versionutils`` from oslo.
+    More information regarding this deprecation can be found in the `patch
+    <https://review.openstack.org/#/c/115423/>`_ that proposed the deprecation.