Feature Idea: Add --config flag and environment variable to set the config file

[jespino]

Summary:
Sometimes you don't want to have the config file in the same place you execute your binary, so having the posibility of specifying the config file through a parameter or through an environment variable can help to address that use case. Also some distrubtions, operating systems, or containers systems can take advantage of that parameter/environment to adapt it to its own requirements.

How important this is to me and why:

Importance: Medium

Use cases:

• Docker storing the config file in /run/secrets
• A Linux distribution storing the config file in /etc/focalboard.

[chenilim]

Agree the config file path should be configurable as a parameter. Putting it up for grabs.

[achie27]

I will be grabbing this.

[jespino]

@achie27 Great! thanks!