Use paratest for parallel test execution

[manuelmeister]

To speed up our api tests, I've parallelized them with paratest. It works quite good. Has to be tested, if it actually tests, as the duration seems fishy

[manuelmeister]

@usu Yes, but you would need to setup the databases

[manuelmeister]

I realized that from https://github.com/ecamp/ecamp3/commit/39410e3045264ed1b731b149591c234f1cec6ac8 (update phpunit from v10.5.20 to v10.5.21, main feature: https://github.com/sebastianbergmann/phpunit/pull/5861) the test only takes 3m 19s, instead of 14m 34s. With my PR it is again reduced to 1m 22s.

[BacLuc]

It seems to be stable, tested it 20 times:

[BacLuc]

@manuelmeister will you finish this change or should i take over?

[manuelmeister]

@BacLuc done