XML Editor - validation status should be persistently stored

Current Situation

• When the user validates an XML configuration and reloads the page then the information that a validation has been performed is lost and the XML configuration is considered not being validated.
• The lifetime of the "valid" status is limited to viewing the current page.

Desired Behavior

• If a validation has been performed then this information should be stored persistently.
  • If an XML configuration is modified later on then it is considered being "not validated".
  • If an XML configuration is not modified later on its status being "validated" remains in place.