// opts specifies the echo call options. When using RunForApps, the To will be set dynamically.
	opts echo.CallOptions
	// setupOpts allows modifying options based on sources/destinations
	setupOpts func(src echo.Caller, opts *echo.CallOptions)
	// check is used to build validators dynamically when using RunForApps based on the active/src dest pair
	check     func(src echo.Caller, opts *echo.CallOptions) echo.Checker