public static DocumentUpdateFlags extractFlags(int combined) {
        return new DocumentUpdateFlags((byte)(combined >> 28));
    }
Class used to represent up to 4 flags used in a DocumentUpdate.
These flags are stored as the 4 most significant bits in a 32 bit integer.

Flags currently used:
  0) create-if-non-existent.

@author geirst
document/src/main/java/com/yahoo/document/serialization/DocumentUpdateFlags.java