specify login_service name
specify login_service name

required for JupyterHub auth page refactor

Xarthisius/oauthenticator,zonca/oauthenticator,santi81/oauthenticator,yuvipanda/mwoauthenticator,willjharmer/oauthenticator,minrk/oauthenticator,luisfdez/oauthenticator,NickolausDS/oauthenticator,Xarthisius/oauthenticator,zonca/cilogonauthenticator,zonca/oauthenticator,luisfdez/oauthenticator,willjharmer/oauthenticator,yuvipanda/mwoauthenticator,zonca/cilogonauthenticator,jupyterhub/oauthenticator,cmclaughlin/oauthenticator,enolfc/oauthenticator,maltevogl/oauthenticator,cmclaughlin/oauthenticator,jupyter/oauthenticator,jupyter/oauthenticator,santi81/oauthenticator