rshiny-server-cmd doesn't allow for additional timeout configurations in shiny server config file

[aditipate]

Currently there is no way to increase the app timeout through command line since the shiny server config is generated by get_server_conf function which only uses the most basic configuration possible. This poses an issue when I try to use rshiny-server-cmd with applications that require longer timeouts. I also have a potential solution for this: PolusAI#2

More specifically, this potential solution:

• Adds additional click options to configure RShiny Server timeouts in the command line:
  • --app-init-timeout which defines the amount of time Shiny Server will wait for an R process to start before giving up.
  • --app-idle-timeout which defines the amount of time an R process will persist with no connections before being terminated
  • --http-keepalive-timeout which defines how long a keepalive connection will sit between HTTP requests/responses before it is closed.