Upgrade to Laravel 9

[mzur]

Laravel 9 was just released as new LTS version. We should upgrade until Laravel 6.x support is dropped on September 6th, 2022. Also check which new features we could use to simplify code:

• Do the upgrade from 6.x to 7.x
• Do the upgrade from 7.x to 8.x
• Do the upgrade from 8.x to 9.x
• Upgrade the Swift adapter to Flysystem 3.x
• Maybe use job batching (e.g. for laser point detection, processing of new images/videos)
• Maybe use the new http client instead of Guzzle directly, which could simplify tests
  • Guzzle isn't used too often. There is too little benefit of changes.
• Maybe use the new artisan test command
  • Too verbose.
• Check out and maybe customize the new markdown mail template
  • No need, they are fine.
• Move model classes to app/Models
  • Too much work. Will be done in Move model classes to own namespace #426.
• Implement model factory classes
• Use migration squashing
  • Maybe not as it could clash with module migrations?
• Use the new rate limiter
• Make sure the rendered paginations are still Bootstrap 3
• Use the new routing namespace definition
  • Too many use statements in the route file for my taste. We'll keep the namespace and string definitions.
• Maybe use enum casting for "static models" (e.g. role, shape)
  • Requires PHP 8.1 and offers little benefit to the existing implementation.
• Use checked/selected Blade directives
• Find a way to enable Psalm linting with the Laravel plugin again (it seems to support only Laravel 6.x and 8.x)
  • Deferred to Enable PHP linting again #427
• Enable API rate limiting by adding the api middleware group to the API routes in the RouteServiceProvider
  • Rate limiting was disabled before so do this carefully. Make an announcement once this is implemented.
• Merge pull requests of modules
• Add migration instructions to release notes