About the styles - sorry! I forgot to show it:
It's possible to define style for a Plain Text control (and also for Table Row / Table cell):
In this case I choose a trivial thing:
You could define several style with conditions, so the first one to evaluate to "true" at run-time is applied.
The text in the Plain Text control could also be a dynamic expression. So combining these two options you could present different text and color according to case:
Please fix input and resubmit for error, or:
A notification item was added successfully.
About the model:
It's best to simplify the error scenario as much as possible.
About the services: we can't to run them internally, but we get the full picture of the flow.
Thanks,
Udi