Support $PORT and $HOSTNAME

[tanner0101]

Support PORT and HOSTNAME environment variables for setting server configuration. These should override the default configured port / hostname when present in the environment. --port and --hostname passed via the CLI should still take precedent.

vapor/api-template#93 (comment)

[gwynne]

@tanner0101 To fully replace the functionality currently found to be unavailable via CMD in Dockerfiles (for multiple reasons), you will also need an ENVIRONMENT, ENV, or (my personal favorite) VAPOR_ENV corresponding to --env.

[tanner0101]

From Discord, these seem like the best options in terms of variable naming:

• LOG_LEVEL
• SERVER_HOSTNAME
• SERVER_PORT
• VAPOR_ENV

[mattpolzin]

Not sure if it’s really worth much to support Heroku out of box but that would come for free with the ENV var named PORT