fix(bigtable): add materialized view routing param to ReadRows and Sa…

[mutianf]

…mpleRowKeys

ReadRows and SampleRowKeys can target a materialized view, but the client's request-params extractor only emitted table_name + app_profile_id and ignored materialized_view_name. Per the google.api.routing annotation in bigtable.proto, materialized views are instance-scoped and must route on the instance name.

Split the header composition into composeReadRequestParams (materialized-view capable) and composeWriteRequestParams (table/authorized-view only), and add NameUtil.extractInstanceNameFromMaterializedViewName.

Add HeadersTest coverage asserting the instance-name routing param for both operations, and a ReadIT integration test that reads through a materialized view.

[gemini-code-assist]

Code Review

This pull request adds support for routing read requests (ReadRows and SampleRowKeys) targeting materialized views in Cloud Bigtable. Since materialized views are instance-scoped, they route on the instance name instead of the table name. The changes introduce helper methods to extract the instance name, update the stub to handle this routing logic, and add corresponding tests. The feedback suggests omitting the app_profile_id parameter from the routing headers when it is empty to maintain consistency with write requests and avoid sending empty parameters to the server.

[gemini-code-assist]

If appProfileId is empty, ImmutableMap.of will still include it as an empty string (i.e., "app_profile_id" -> ""). In contrast, composeWriteRequestParams omits the app_profile_id key entirely when it is empty. To maintain consistency and avoid sending an empty routing parameter to the server, we should omit app_profile_id when it is empty.

Suggested change

	if (!materializedViewName.isEmpty()) {
	return ImmutableMap.of(
	"name",
	NameUtil.extractInstanceNameFromMaterializedViewName(materializedViewName),
	"app_profile_id",
	appProfileId);
	}
	if (!materializedViewName.isEmpty()) {
	String instanceName =
	NameUtil.extractInstanceNameFromMaterializedViewName(materializedViewName);
	if (appProfileId.isEmpty()) {
	return ImmutableMap.of("name", instanceName);
	}
	return ImmutableMap.of("name", instanceName, "app_profile_id", appProfileId);
	}

[mutianf]

wrong