Make Registrant/Registrar use same TARA controller

app/controllers/sso/tara_controller.rb

@@ -0,0 +1,40 @@
+module Sso
+  class TaraController < ApplicationController
+    skip_authorization_check
+
+    def registrant_callback
+      user = RegistrantUser.find_or_create_by_omniauth_data(user_hash)
+      callback(user, registrar: false)
+    end
+
+    def registrar_callback
+      user = ApiUser.from_omniauth(user_hash)
+      callback(user, registrar: true)
+    end
+
+    # rubocop:disable Style/AndOr
+    def callback(user, registrar: true)
+      session[:omniauth_hash] = user_hash
+      (show error and return) unless user
+
+      flash[:notice] = t(:signed_in_successfully)
+      sign_in_and_redirect(registrar ? :registrar_user : :registrant_user, user)
+    end
+    # rubocop:enable Style/AndOr
+
+    def cancel
+      redirect_to root_path, notice: t(:sign_in_cancelled)
+    end
+
+    def show_error(registrar: true)
+      path = registrar ? new_registrar_user_session_url : new_registrant_user_session_url
+      redirect_to path, alert: t(:no_such_user)
+    end
+
+    private
+
+    def user_hash
+      request.env['omniauth.auth']
+    end
+  end
+end