added validation for photo value to check if a valid file resource is set
fixed regex for validating a photo
wrote error message transform for multi value attribute types
fixed null value behaviour
fixed tests du to validation changes
added negative tests to check canonical type violations
fixed some tests
Merge remote-tracking branch 'origin/validation' into validation
wrote some tests
refactored test
added message transformer for json validation
fixed overwriting
fixed error
Merge remote-tracking branch 'origin/validation' into validation
fixed regex for error mapping
fixed regular expression for an exception message with a newline it, thanks jackson ...
removed unnecessary message transformer
fixed typo
added message formatter and tests for invalid json list syntax
Merge remote-tracking branch 'origin/validation' into validation