Action to be taken before rendering the edit page.
Configuration can be modified by this method.
Example use is verifying configuration so that proper warnings can be displayed before user takes any action.
configuration - configuration to be loaded into the UI
Action to be taken before repository is saved from the UI. The method is called after the validate() method and only
if validation is successful. If this method returns with error the configuration is not saved.
Configuration can be modified by this method and the changes will be persisted.
collection of error messages. Should be empty if call is successful.