//TODO


 - background job for re-delivery
 - accept/decline subscriptions (PATCH subs)
 - (message.go) api routes
 - (compat.go) api routes
 - https://firebase.google.com/docs/cloud-messaging/send-message#rest
 - List subscriptions on owned channels /RESTful?)
 - deploy
 - Dockerfile
 - php in html
 - full-text-search: https://www.sqlite.org/fts5.html#contentless_tables