mergeOid function
Creates a new OID based two OIDs.
NOTE: requires oid1 and oid2 to be at least 12 chars long.
Implementation
String mergeOid(String oid1, String oid2) {
assert(isValidOid(oid1), oid1);
assert(isValidOid(oid2), oid2);
return "${oid1.substring(0, 12)}${oid2.substring(_lenTimePart, 12 + _lenTimePart)}";
}