add roles editor and supervisor in roles model

app/models/role.rb

@@ -33,4 +33,13 @@ class Role < ApplicationRecord
   def self.moderator
     find_by(name: 'moderator') || create!(name: 'moderator')
   end
+
+  def self.editor
+    find_by(name: 'editor') || create!(name: 'editor')
+  end
+
+  def self.supervisor
+    find_by(name: 'supervisor') || create!(name: 'supervisor')
+  end
+  
 end