allow for initializers to draw their values from environment variables

[elrayle]

A lot of application customization happens in initializers (e.g. /config/initializers/qa.rb and qa_server.rb). From these files, you can configure colors for graphs, whether to show graphs or data tables or both, the time period behind these, time zone, caching controls, etc. To allow these to be easily set, the values in the initializers will be drawn from environment variables that are set in .env.

• update .env.example to show which can be configured
• update initializers to draw values from .env, keeping current values as defaults if an environment variable isn't setup

Related work

Already customizable...

• which authorities to use - by loading on to EFS drive (I believe this would allow for local authorities defined in yaml files.)
• .env file - by putting in S3 bucket

May also want to consider how an application would customize...

• css
• i18n (most notably application name and version) - Issue how to handle localization file #37
  • for application name and version, may want to move that to environment variables
• how to install custom modules - Issue Get Wikidata auth working in the container #12
• how to add nav menu customizations - Issue Customization: allow additional items in nav menu #46

Questions

• Where do graphs go when they are generated?