fix admin_generator rake task to avoid duplicates

Author: crohr

lib/tasks/admin_generator.rake

@@ -1,8 +1,10 @@
 # desc "Explaining what the task does"
 task admin_generator: :environment do
   app = App.first
-  app.add_admin(Agent.create(
-                  email: ENV['ADMIN_EMAIL'],
-                  password: ENV['ADMIN_PASSWORD']
-                ))
-end
+  if app.app_users.where(role: "admin", email: ENV['ADMIN_EMAIL']).none?
+    app.add_admin(Agent.create(
+                    email: ENV['ADMIN_EMAIL'],
+                    password: ENV['ADMIN_PASSWORD']
+                  ))
+  end
+end