Introduce end to end tests

[Art4]

This PR introduces end to end (e2e) tests. This tests allows us to use the locally installed Redmine server from #336 to run API requests against it. This helps us to test, understand and reverse engineer the behavior and responses of different Redmine versions. I've used this method to check the group features in #359. And I will use this tests to implement the new endpoints to close/archive a project (#192).

To run the tests you have to start the docker container. This will setup the Redmine server and database. I switched from MariaDB to SQLite btw.

docker compose build
docker compose up -d

To install all dependencies of php-redmine-api run:

docker compose exec -u 1000 php composer update

The end2end tests can be run with:

docker compose exec -u 1000 php composer run end2end

I was not able to run this tests in Github Actions, so if anybody has some hints for me this would be great.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (19d3eb5) 96.72% compared to head (44226fc) 96.72%.

Additional details and impacted files

@@            Coverage Diff            @@
##               v2.x     #360   +/-   ##
=========================================
  Coverage     96.72%   96.72%           
  Complexity      534      534           
=========================================
  Files            27       27           
  Lines          1467     1467           
=========================================
  Hits           1419     1419           
  Misses           48       48           

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