async salt functions.

[whytewolf]

This plugin should really support the async client/runner functions in salt-api. As currently, long-running calls are going to run into timeout issues, no matter what you set the rest_timeout to.

See https://docs.saltstack.com/en/latest/ref/netapi/all/salt.netapi.rest_cherrypy.html#best-practices

[girstenbrei]

Correct me if I'm wrong, but it seems like this is what is happening when using blockbuild: true for the command, there is source code and a test for it.
If this is true, maybe just some missing docs about it?

[mturra-Pro]

I launch a long orchestration with "Client Interface": runner and I get back a "504 Gateway Timeout" from cherrypy.
Salt-api support async orchestration with client=runner_async. The plugin today doesn't have this option.
And doesn't support salt-api events to intercept when the async job terminates.
See: https://docs.saltproject.io/en/latest/ref/netapi/all/salt.netapi.rest_cherrypy.html#best-practices