feat(install): 3 routes to install key (with key name, without key name and else install all keys)

For example:
/stanislas.chollet@gmail.com/install (Install default key)
/stanislas.chollet@gmail.com/work/install (Install key 'work')
/stanislas.chollet@gmail.com/all/install (Install all user keys)
doc(upload): Add missing documentation about the 'keypath' parameter