controller/metadata: New metadata controller.

Add new metadata controller with an incomplete implementation
of the first endpoint.

BUG=b:194405049
TEST=manually ran endpoint

Change-Id: I6e9c5cff8beab8a0ea00bb4c2c621b6a8a800bb9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3273767
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Lizzy Presland <zland@google.com>
Commit-Queue: Alex Klein <saklein@chromium.org>
diff --git a/api/router.py b/api/router.py
index 0e5a43d..a89773b 100644
--- a/api/router.py
+++ b/api/router.py
@@ -27,6 +27,7 @@
 from chromite.api.gen.chromite.api import depgraph_pb2
 from chromite.api.gen.chromite.api import firmware_pb2
 from chromite.api.gen.chromite.api import image_pb2
+from chromite.api.gen.chromite.api import metadata_pb2
 from chromite.api.gen.chromite.api import packages_pb2
 from chromite.api.gen.chromite.api import payload_pb2
 from chromite.api.gen.chromite.api import sdk_pb2
@@ -430,6 +431,7 @@
   router.Register(depgraph_pb2)
   router.Register(firmware_pb2)
   router.Register(image_pb2)
+  router.Register(metadata_pb2)
   router.Register(packages_pb2)
   router.Register(payload_pb2)
   router.Register(sdk_pb2)