How do I find a model for Refinery's built-in users in Rails -

i using refinery , want make edits refineryuser. in schema file see following:

  create_table "refinery_authentication_devise_users", force: :cascade |t|     t.string   "username",               null: false     t.string   "email",                  null: false     t.string   "encrypted_password",     null: false     t.datetime "current_sign_in_at"     t.datetime "last_sign_in_at"     t.string   "current_sign_in_ip"     t.string   "last_sign_in_ip"     t.integer  "sign_in_count"     t.datetime "remember_created_at"     t.string   "reset_password_token"     t.datetime "reset_password_sent_at"     t.datetime "created_at"     t.datetime "updated_at"     t.string   "slug"     t.string   "full_name"   end 

but cannot find model. how find model can add callbacks, validations, , other code refineryusers. may add activeadmin , make refinery user activeadmin user.

user models stands in https://github.com/refinery/refinerycms-authentication-devise if use extension. if use activeadmin, have hack it: https://github.com/refinery/refinerycms-authentication-devise/issues/16