What you are doing is searching for a specific set of users. With a query parameter within your URL, you can achieve this.
To return a single user (id is 5):
/usermanagement/users/5
To return all users:
/usermanagement/users
To return a set of users based on search:
/usermanagement/users?username=
That way, your API is open to searching by a specified criteria which can also be extended.
Say, you wish to search by location:
/usermanagement/users?location=
Say, you wish to combine these:
/usermanagement/users?username={criteria}&location={criteria}
You may also want to expose a search endpoint itself:
/usermanagement/search
You might find other options here too:
RESTful URL design for search