fix: Prevent lock with unsaved changes (#1640)

Author: btagliani

app/controllers/devise_token_auth/sessions_controller.rb

@@ -131,7 +131,7 @@ def resource_params
     end
 
     def create_and_assign_token
-      if @resource.respond_to?(:with_lock)
+      if @resource.respond_to?(:with_lock) && !@resource.changed?
         @resource.with_lock do
           @token = @resource.create_token
           @resource.save!