Protocol Engine: Allow starting and pausing a JSON protocol over HTTP

[sanni-t]

As a user, I want to be able to reliably and predictably start and pause my running JSON protocol over HTTP.

• When a play POST request is sent to the robot server, the protocol should start executing the commands from the beginning.

  • Implementation details:
    • A new ID for the action is generated and appended to commands/actions list.
    • PE state & session state are updated
    • CommandQueueWorker starts a task to fetch and execute the next command in the protocol

• The server should respond with either an action successful or unsuccessful response with explanation

  • If successful, respond with the action ID (& updated session state?)
  • If unsuccessful, respond with appropriate error messages.

• When a pause POST request is sent to the robot server, the protocol should pause execution in a way that makes it possible to resume the protocol reliably.

  • Implementation details:
    • A new ID for the action is generated and appended to commands/actions list.
    • PE state & session state are updated
    • CommandQueueWorker stops its fetch task
    • The last command that was executing before pause is received is completed. Next command is not fetched. [NOTE: This behavior could change depending on UX spike results]
    • This behavior is coarser than the current implementation of pause. refactor(engine): pause HardwareAPI when engine is paused #7923 will address updating this behavior.

• The server should respond with either an action successful or unsuccessful response with explanation

  • If successful, respond with the action ID (& updated session state?)
  • If unsuccessful, respond with appropriate error messages.