Environment variables

[bigheadsmith]

• FORCE_TO_EXPLICITLY_SELECT_TYPE_WHEN_REQUESTING_NEW_LEAVE environment variable does not appear to be handled correctly.
  A select option is not added to book_leave_type_modal regardless of the value.
  It does however work if adjusting the variable in config/app.json

• Similar issue with OPTION_ALLOW_NEW_REGISTRATIONS
  Seems to work as desired by changing .env and login.js to OPTIONS_REGISTRATION
  this was just me knot rebuilding the docker image after changing the value

• Do other environment variables need to be checked to ensure they are handled as expected if they are passed as arguements, set in .env, or set in config/app.json?

• I believe it is something to do with underscores in the variable names, as underscore is used as the separator in lib/config.js