public String toStringWithQualifier() {
    return toString(true);
  }
Stringifies the {@link ImageReference}. If the digest is set, the result will include the
digest and no tag. Otherwise, the result will include the tag, or {@code latest} if no tag is
set.

@return the image reference in Docker-readable format including a qualifier.
jib-core/src/main/java/com/google/cloud/tools/jib/api/ImageReference.java