[FlightSQL] Allow implementations of FlightSqlService to handle custom actions and commands

[amartins23]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

The current FlightSqlService trait allows the implementer to handle custom commands in the DoGet call via do_get_fallback method implementation. However, no such possibility is offered for DoPut, DoAction and ListActions.

A similar case could be made for DoExchange.

Describe the solution you'd like

Create new methods (with default implementations) in the FlightSqlService trait: do_put_fallback, do_action_fallback, with equivalent behavior as the do_get_fallback method. Furthermore, add a method that enables the implementation of the FlightSqlService trait to fill in additional actions to the actions returned by ListActions (

arrow-rs/arrow-flight/src/sql/server.rs

Lines 608 to 617 in 0bcf200

	let actions: Vec<Result<ActionType, Status>> = vec![
	Ok(create_prepared_statement_action_type),
	Ok(close_prepared_statement_action_type),
	Ok(create_prepared_substrait_plan_action_type),
	Ok(begin_transaction_action_type),
	Ok(end_transaction_action_type),
	Ok(begin_savepoint_action_type),
	Ok(end_savepoint_action_type),
	Ok(cancel_query_action_type),
	];

), maybe named add_custom_actions that adds the actions to the existing vector, or a list_custom_actions that returns a (optional) vector that is appended to the existing vector.

Describe alternatives you've considered

The alternative is to create a wrapper FlightService implementation that has custom handling, then forwards everything to the existing implementation provided by implementing FlightSqlService.

Additional context