coder_app shall allow docker network scoped urls other than localhost

[amirhmoradi]

Use case:
I want to add a coder_app which opens another container's url instead of being limited to http:/:localhost:[PORT]/[SUBPATH] :
(Of course, both containers are part of the same docker network, and the url resolve correctly when using curl.)

example:

resource "coder_app" "auth_phpmyadmin" {
  agent_id            = coder_agent.workspace.id
  slug                = "pma-auth"
  icon                = "https://www.phpmyadmin.net/static/images/logo.png"
  url                 = "http://other-container-phpmyadmin:80/" 
  subdomain           = true
  share               = "authenticated"

}