Optimize/rework the build_user_list helper function

[jjnesbitt]

multinet-api/multinet/api/views/workspace.py

Lines 28 to 40 in 11fc729

	def build_user_list(validated_data: OrderedDict) -> list:
	"""
	Build a list of user objects from an ordered dictionary of user data.
	Accepts an ordered dictionary containing a list of validated user data, e.g.
	as a result of validating a PermissionsSerializer with request data.
	Returns a list of user objects.
	"""
	user_list = []
	for valid_user in validated_data:
	user_object = get_object_or_404(User, username=valid_user['username'])
	user_list.append(user_object)
	return user_list

This function is used to create user objects from usernames, but does so by fetching user objects from the database in a loop. This is inefficient, and should be done in bulk. The main question is how username that are not found should be handled and errors returned to the endpoint. One idea I had was to do a filter on User objects to return the full users, and for any usernames not in the returned list, we can raise an error stating that they do not exist.