Adding a final class

"..If a nonfinal class implements a constant interface, all of its subclasses will have their namespaces polluted by the constants in the interface."

url - https://ci.openmrs.org/sonar/drilldown/issues/1865?rids%5B%5D=2245&rule=squid%3AS1214&rule_sev=MINOR&severity=MINOR#