Configuration externalization

[juliendangers]

To avoid having to create a specific file for each environment, and to be able to deploy multiple freight-server instances with different configurations, it is easier to be able to provide configuration from environment variables. It is also easier to use with docker

I still need to find a way to extract redis options, but file can used for that at the moment.

I still need to update README to explain password is empty by default, and I may need to update tests accordingly (I'll do it today).

[vladikoff]

Anything else you wanted in this PR? Redis config?

[juliendangers]

@vladikoff do you think it's a good idea to drop automatic password generation ? Shouldn't we generate one if not set in env variable or configuration file ?

[vladikoff]

@vladikoff do you think it's a good idea to drop automatic password generation ? Shouldn't we generate one if not set in env variable or configuration file ?

Yeah I like the functionality, can we keep it?

[juliendangers]

👍 I could try to generate a new password if it's not set through env variable or configuration file