Resolves sites from a YAML file loaded once into :persistent_term.

alpha:
  theme: alpha
  hosts: [alpha.example.com]
  locale: en
  settings:
    title: Alpha

Add it to your supervision tree so the file is loaded at boot:

{Multitenancy.SiteResolver.YAML, path: Application.app_dir(:my_app, "priv/sites.yml")}