Specify patchable type

## OpenProject Work Packages

* https://community.openproject.org/work_packages/17420
* https://community.openproject.org/work_packages/17421
* https://community.openproject.org/work_packages/17422

## Changes

* type linked in WP rather than named
* new endpoints
    * type by id
    * all types
    * type by project
* project links to available types
For the record: We discussed that I will remove embedding that is optional from the examples (more concise, less work for me :D )

But we also agreed that I will do that in a later PR, not in this one.