[Cosmos] make PartitionKeyType public, mark excluded locations as sequence, make InternalException private

[simorenoh]

Tackling some of the bullet points from the api review for our next GA release: #43211

Items tackled here:

• re-add SERVICE_UNAVAILABLE = 503 to the constants file - it was probably removed due to it being un-used, but it will now have special casing with PPAF anyway
• new InternalException should be marked as private by using an underscore, since it should not be something for users to use
• update the typing of excluded_locations: Optional[list[str]] to excluded_locations: Optional[Sequence[str]] across the SDK
• _PartitionKeyType was made private - which doesn't make sense if it applies to all the public APIs that use partition keys. we should likely expose this instead

[Copilot]

Pull Request Overview

This PR makes the previously internal partition key type alias public and broadens excluded_locations parameter annotations from concrete lists to more general sequences, plus a small internal variable rename for clarity.

• Exposes PartitionKeyType (removes leading underscore) and updates all references.
• Updates excluded_locations annotations/docstrings from List[str] to Sequence[str].
• Renames a local variable in partition health tracking for clearer semantics.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
partition_key.py	Makes PartitionKeyType public by removing underscore.
container.py	Replaces usages of _PartitionKeyType with PartitionKeyType; widens excluded_locations type hints/docstrings to Sequence.
aio/_cosmos_client_connection_async.py	Async equivalents updated to public PartitionKeyType and Sequence annotations.
aio/_container.py	Async container updates similar to sync version.
_read_items_helper.py	TYPE_CHECKING imports and annotations updated to PartitionKeyType.
_query_builder.py	TYPE_CHECKING annotations updated to PartitionKeyType.
_partition_health_tracker.py	Renames internal variable excluded_locations to unhealthy_locations for clarity.
_cosmos_client_connection.py	Updates to PartitionKeyType; adjusts internal query plan method parameter typing.

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

azure-cosmos

[allenkim0129]

LGTM

[allenkim0129]

LGTM

[simorenoh]

/azp run python - cosmos - ci

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[simorenoh]

/check-enforcer override