feat(bigtable): support materialized views in the data client (#17676)

## Summary

Adds materialized view support to the Bigtable data client, alongside
the existing `Table` and `AuthorizedView` surfaces:

- New `MaterializedView` / `MaterializedViewAsync` classes (subclasses
of `_DataApiTarget`) and a `client.get_materialized_view(instance_id,
materialized_view_id)` factory. Reads (`read_rows*`, `sample_row_keys`,
`row_exists`) route requests via the `materialized_view_name` field.
- Materialized views are read-only in the Bigtable API — the mutation
RPCs have no `materialized_view_name` field — so `mutate_row`,
`bulk_mutate_rows`, `check_and_mutate_row`, `read_modify_write_row`, and
`mutations_batcher` are overridden to raise `NotImplementedError`
immediately instead of failing with an opaque proto error (or, for the
batcher, failing later in a background flush).
- Since materialized views are instance-scoped and have no backing
table, table identity (`table_id`/`table_name`) moves from the shared
`_DataApiTarget` base class into the `Table` and `AuthorizedView`
subclasses. Public constructor signatures are unchanged.
- Sync surfaces regenerated via `nox -s generate_sync`; docs pages added
for both new classes.

## Test plan

- [x] Unit tests: new `TestMaterializedView` suites (async + generated
sync) cover construction, routing metadata (`name=<instance path>`
header), factory passthrough, context-manager use, and the
mutation-method rejection; `get_materialized_view` added to the existing
API-surface parametrizations
- [x] Full `tests/unit` suite passes locally (5394 passed)
- [x] Manually exercised against a local gRPC server:
`ReadRows`/`SampleRowKeys` requests carry `materialized_view_name` (not
`table_name`), rows are returned through the public API, and
`Table`/`AuthorizedView` behavior is unchanged
- [ ] CI (docs build, lint, sync-up-to-date check across supported
Python versions)

---------

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

Author: axyjo

packages/google-cloud-bigtable/docs/data_client/async_data_materialized_view.rst

@@ -0,0 +1,11 @@
+Materialized View Async
+~~~~~~~~~~~~~~~~~~~~~~~
+
+    .. note::
+
+      It is generally not recommended to use the async client in an otherwise synchronous codebase. To make use of asyncio's
+      performance benefits, the codebase should be designed to be async from the ground up.
+
+.. autoclass:: google.cloud.bigtable.data._async.client.MaterializedViewAsync
+  :members:
+  :inherited-members:

packages/google-cloud-bigtable/docs/data_client/data_client_usage.rst

@@ -10,6 +10,7 @@ Sync Surface
   sync_data_client
   sync_data_table
   sync_data_authorized_view
+  sync_data_materialized_view
   sync_data_mutations_batcher
   sync_data_execute_query_iterator
 
@@ -22,6 +23,7 @@ Async Surface
   async_data_client
   async_data_table
   async_data_authorized_view
+  async_data_materialized_view
   async_data_mutations_batcher
   async_data_execute_query_iterator
 

packages/google-cloud-bigtable/docs/data_client/sync_data_materialized_view.rst

@@ -0,0 +1,6 @@
+Materialized View
+~~~~~~~~~~~~~~~~~
+
+.. autoclass:: google.cloud.bigtable.data._sync_autogen.client.MaterializedView
+  :members:
+  :inherited-members:

packages/google-cloud-bigtable/google/cloud/bigtable/data/__init__.py

@@ -19,6 +19,7 @@
 from google.cloud.bigtable.data._async.client import (
     AuthorizedViewAsync,
     BigtableDataClientAsync,
+    MaterializedViewAsync,
     TableAsync,
 )
 from google.cloud.bigtable.data._async.mutations_batcher import MutationsBatcherAsync
@@ -33,6 +34,7 @@
 from google.cloud.bigtable.data._sync_autogen.client import (
     AuthorizedView,
     BigtableDataClient,
+    MaterializedView,
     Table,
 )
 from google.cloud.bigtable.data._sync_autogen.mutations_batcher import MutationsBatcher
@@ -80,10 +82,12 @@
     "BigtableDataClientAsync",
     "TableAsync",
     "AuthorizedViewAsync",
+    "MaterializedViewAsync",
     "MutationsBatcherAsync",
     "BigtableDataClient",
     "Table",
     "AuthorizedView",
+    "MaterializedView",
     "MutationsBatcher",
     "RowKeySamples",
     "ReadRowsQuery",