A GenServer that manages a streaming function call.

This process is responsible for executing a function that returns a stream of results, and sending those results back to the client in chunks via {:stream_response, response} messages.

Lifecycle

1. Started via start_link/1 with a %FunConfig{}, %Request{}, and receiver pid.
2. On init, immediately starts the stream via handle_continue(:start_stream, ...).
3. The MFA is called through Executor.sync_call/2.
4. If the result is an error, sends a single error response and stops.
5. If successful, sends the initial chunk and waits for further messages.
6. The data generator sends {:result, data} for intermediate chunks, {:last_result, data} for the final chunk, or {:error, reason} on failure.
7. On :complete or :stop, sends a stream-end response and stops.

Messages to Data Generator

The stream process expects these messages from the data generator:

• {:result, data} — Intermediate chunk (sets has_more: true)
• {:last_result, data} — Final chunk (sets has_more: false)
• {:error, reason} — Error (sends error response)
• :complete — Normal completion (sends stream-end response)

Stopping

Use stop/1 with either the stream PID or the request_id to gracefully terminate a stream. This sends a completion response before stopping.