Added failing specs for API watcher resource
Add watchers#create API end point
Render API error response when watcher is invalid
Let API render status 200 if a user is already a watcher
Add authorization to API watchers#create
Implement API watchers#delete end point
Remove duplicate code block
Add watch and unwatch links to wp resource (WIP)


TODO
	- fix specs
	- prettify code
SASS change for watch / unwatch WP
Allow users allowed to view work packages to (un-)watch via API v3 (WIP)


TODO better code style
Services for watcher creation / removal
Use type coercion to convert id params
Merge branch 'feature/adding-and-removing-watchers' of github.com:opf/openproject into feature/adding-and-removing-watchers
Remove accidentally added comma
Watch / unwatch work packages
Display delete button next to watchers in details tab
Merge branch 'feature/adding-and-removing-watchers' of github.com:opf/openproject into feature/adding-and-removing-watchers
Merge branch 'feature/adding-and-removing-watchers' of github.com:opf/openproject into feature/adding-and-removing-watchers
Avoid error when representer is initialized without current user
Spec presence of (un-)watch link in representer spec