feat(sdk): Implement Registry client (kubeflow#7597)

* Implement registry client

* Update registry client code

* Add test skeleton

* Add some tests

* Update code

* add tests

* update tests

* update tests

* Rename Client -> RegistryClient

* Update wrt comments

* add type annotations

* fix renaming in __init__.py

* remove unused imports

* extract host variable in test

* format using yapf

* remove locals and use arg keywords

* remove json conversion

* fix header

* write bytes when downloading file

* fix create_tag; fix tests

* fix request_body for update_tag and create_tag using json.dumps

* simply return json for delete_tag

* rename files

* format files

* update return types and format double quotes

* add comments and format files

* add todos

* update credentials and change open to use context

* format using yapf

* move request into context

* Update comments

* Update release notes

* Update release notes

sdk/RELEASE.md

@@ -68,6 +68,7 @@
 # 2.0.0-alpha.0
 
 ## Major Features and Improvements
+* feat(sdk): Implement Registry Client [\#7597](https://github.com/kubeflow/pipelines/pull/7597)
 
 ## Breaking Changes
 

sdk/python/kfp/registry/__init__.py

@@ -0,0 +1,16 @@
+# Copyright 2022 The Kubeflow Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from kfp.registry.registry_client import ApiAuth
+from kfp.registry.registry_client import RegistryClient