Move artifact validation out of the domain layer into the MavenPublisher service layer
Disallow empty string values for MavenArtifact extension and classifier (allow null)
- Handle null values in MavenPublisher
Validate IvyArtifacts in service layer when publishing
- Moved some checks from domain into ValidatingIvyPublisher
- Added some validation for artifact attributes
Include publication name in validation error messages when publishing