[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