0.323.0

This release adds an on_stream_result hook to SchemaExtension for extension
authors who need to inspect or mutate GraphQL results before they reach a
streaming transport.

The hook wraps subscription events and queries or mutations sent over WebSockets,
SSE, or multipart responses. On transports that support experimental incremental
execution, it also wraps each incremental-delivery frame.

Strawberry's built-in MaskErrors extension now uses the hook so streamed query,
mutation, subscription, incremental-delivery, and pre-execution errors are masked
before being sent to clients.

This release was contributed by @Ladol in #4330

Additional contributors: @pre-commit-ci[bot], @patrick91