Summary

Fix Snapserver.stream_control() so command-specific parameters are sent in the nested params object expected by Snapserver's Stream.Control JSON-RPC API.

The current implementation passes control_params into _request() as a generic parameters mapping, which causes values such as position or offset to be flattened into the top-level request parameters.

This means parameterless commands such as play, pause, playPause, stop, next, and previous can work, while parameterized commands such as seek and setPosition are sent with an invalid payload.

Current behavior

A call such as:

await server.stream_control(
    "stream",
    "setPosition",
    {"position": 12.5},
)

currently produces the equivalent of:

{
  "id": "stream",
  "command": "setPosition",
  "position": 12.5
}

Snapserver expects:

{
  "id": "stream",
  "command": "setPosition",
  "params": {
    "position": 12.5
  }
}

Changes

This PR sends control arguments under the required nested params key, makes control_params optional, defaults parameterless commands to "params": {}, preserves the existing parameterless transport controls, and enables correctly formatted seek and setPosition requests.

Tests

Adds regression tests for the exact JSON-RPC payload generated for:

• a parameterless pause command
• a parameterized setPosition command

The tests verify that Stream.Control requests match the format expected by Snapserver.