feat: Consistency polling + restore table for sync client in admin (#1117)

* feat: Prototyped handwritten layer

* Added newlines

* linting

* Added docstrings for restore table and consistency token polling;
removed gc_rule

Author: gkevinzheng

google/cloud/bigtable/admin_v2/overlay/__init__.py

@@ -0,0 +1,45 @@
+# Copyright 2025 Google LLC.
+#
+# 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.
+#
+# This directory and all its subdirectories are the only handwritten
+# components of the otherwise autogenerated google/cloud/bigtable/admin_v2.
+# The purpose of the overlay directory is to add additional functionality to
+# the autogenerated library while preserving its developer experience. These
+# handwritten additions currently consist of the following:
+#
+#  1. TODO: Document final GcRule design choice here
+#  2. An LRO class for restore_table that exposes an Operation for
+#     OptimizeRestoreTable, if that LRO exists.
+#  3. New methods (wait_for_consistency and wait_for_replication) that return
+#     a polling future class for automatically polling check_consistency.
+#
+# This directory is structured to mirror that of a typical autogenerated library (e.g.
+# services/types subdirectories), and the aforementioned handwritten additions are 
+# currently implemented as either types under overlay/types or in methods in an overwritten
+# client class under overlay/services.
+
+from .types import (
+    RestoreTableOperation,
+    CheckConsistencyPollingFuture,
+)
+
+from .services.bigtable_table_admin import (
+    BigtableTableAdminClient,
+)
+
+__all__ = (
+    "RestoreTableOperation",
+    "CheckConsistencyPollingFuture",
+    "BigtableTableAdminClient",
+)

google/cloud/bigtable/admin_v2/overlay/services/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2025 Google LLC.
+#
+# 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.

google/cloud/bigtable/admin_v2/overlay/services/bigtable_table_admin/__init__.py

@@ -0,0 +1,19 @@
+# Copyright 2025 Google LLC.
+#
+# 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.
+
+# TODO: Add the async client after owlbot changes.
+
+from .client import BigtableTableAdminClient
+
+__all__ = ("BigtableTableAdminClient",)