Stackl shouldn't give response "instance creating" when it is not

[GBrawl]

When Stackl for some reason can't create a stack instance E.G. no infrastructure targets are found with OPA. It should let the user know it failed.

[SvenAkk]

This is part of the failure handling upgrade which we tackle in the May Objective

[GBrawl]

OPA error now gets returned when it can't find a target