[META] phase 4

[oliverklee]

• [ ] upgrade phpstan
• [ ] REST action: subscriber info
• [ ] REST action: delete subscriber
• [ ] REST action: update subscriber
• [ ] REST action: create list
• [ ] REST action: list of subscriptions for subscriber
• [ ] REST action: list of subscriptions for list
• [ ] REST action: create subscription
• [ ] REST action: update subscription
• [ ] REST action: delete subscription
• [ ] REST action: info for subscription
• [ ] research HAL JSON API
• [ ] drop the DI class and load the services via composer.json instead
• [ ] decide on what to log
• [ ] log things
• [ ] read up on REST formats
• [ ] support HTTP caching (last modified header, eTag, HEAD requests?), also research whether and how to use and set “valid until” headers
• [ ] research GraphQL
• [ ] investigate Symfony filters for authentication
• [ ] performance testing to have some numbers
• [ ] add a REST route for /api/
• [ ] add a REST route for /api/v2/
• [ ] investigate https://scrutinizer-ci.com/ and maybe use it
• [ ] investigate https://swagger.io/
• [ ] use stylecio to fix the style in PRs
• [ ] delete the old rewrite