Extract request for patch endpoint
Test response for unauthorized user
Test work package update for valid attributes
Set writeable WP attributes
Re-activate WP patch endpoint

This commit reverts 450a8ec1 and c5fe2f63
Test write permissions for WP parent
Authorize parent id update
Validate new parent id
Correct supported operations
Add description for WP's parent id attribute
Update WP patch example request
hide parent manipulation controlls if user lacks permission
harmonize error message

This is the way all error messages are returned for now
Merge pull request #2077 from opf/fix/16875_adding_deleting_parent_and_child_relations_not_working_in_details_pane