Set initial DM_SEARCH_API_AUTH_TOKENS value to None
Set initial DM_SEARCH_API_AUTH_TOKENS value to None

Flask only looks up environment variables for flags defined in the
config, so to get the production environment to be applied the key
should have an initial value in the common preview, staging and
production config.

alphagov/digitalmarketplace-search-api,alphagov/digitalmarketplace-search-api