Create authservice to check if user is allowed to login via this route
Move methods to services to avoid duplicate code in auth/url.js and adminUrl.js
Note: this route is applicable for every client, so we don't need to create an extra client for this login type
Note2: This is the url: /auth/admin/login?clientId=[clientId]&redirect_uri=[redirect_uri]. Maybe it's a good idea to make a redirect (/auth/admin/login?) in the frontend (and admin panel) like we already have for the auth/login route
Note: this route is applicable for every client, so we don't need to create an extra client for this login type Note2: This is the url: /auth/admin/login?clientId=[clientId]&redirect_uri=[redirect_uri]. Maybe it's a good idea to make a redirect (/auth/admin/login?) in the frontend (and admin panel) like we already have for the auth/login route