Contributing

Coding guide lines

Make sure your code follows the PSR-12 code style and is .editorconfig valid. You may use composer run phpcs and Editorconfig-Checker to verify that.
Use use statements wherever possible instead of writing the fully qualified name.
Order the composer/npm dependencies alphabetically.
Do not use code from the includes directory anywhere else.
Please cover your code by unit tests, our goal is to stay at 100% line coverage. Code under includes does not require tests as it's mostly not testable and needs to be rewritten.
Do not use vendor prefixes like -webkit in styles. This is done by PostCSS + Autoprefixer according to the .browserslistrc.
Translations must be abbreviated, for example form.save. The default.po files contain translations that can be auto-detected using Poedit, additional.po contains generated messages like validations.

The PR should contain a short overview of the changes.
Before implementing bigger changes, please open an issue to discuss the feature and possible implementation options.
Please create single pull requests for every feature instead of creating one big monster of pull request containing a complete rewrite.
Squash similar commits to make the review easier.
For visual changes, include both before and after screenshots to easily compare and discuss changes.

The commit message must be meaningful. It should serve as a short overview of the changes. If needed, an additional description can be provided.
A commit should be self-contained and result in a working Engelsystem.