added api endpoint for registrar login

app/controllers/repp/v1/registrar/login_controller.rb

@@ -0,0 +1,22 @@
+module Repp
+  module V1
+    module Registrar
+      class LoginController < BaseController
+        api :GET, 'repp/v1/registrar/login'
+        desc 'check login user and return data'
+
+        def index
+          @login = current_user
+
+          # rubocop:disable Style/AndOr
+          render_success(data: nil) and return unless @login
+          # rubocop:enable Style/AndOr
+
+          data = @login.as_json()
+
+          render_success(data: data)
+        end
+      end
+    end
+  end
+end