info.magnolia.wcs.integration.form.PersonUpdateFormProcessor#personServiceCall
info.magnolia.wcs.integration.form.PersonRegistrationFormProcessor#personServiceCall
info.magnolia.wcs.integration.form.AddressBookFormProcessor#newAddressActionProcess
info.magnolia.wcs.integration.form.AddressBookFormProcessor#editAddressActionProcess
info.magnolia.wcs.integration.form.AddressBookFormProcessor#removeAddressActionProcess
...

All these methods have hardcoded error message if rest service call failed. Instead of hardcoded message we should use error message from rest service which contains reason why call failed.

e.getResponse().readEntity(ObjectNode.class).findValue("errorMessage").asText();