Opcreds: Check for invalid admin subject (#30826)

Moving this check to before the fabric gets added so that the
changes do not have to be backed out if this is invalid.

see #30799

This will be checked in TC-OPCREDS-3.1 (under development)

src/app/clusters/operational-credentials-server/operational-credentials-server.cpp

@@ -641,6 +641,10 @@ bool emberAfOperationalCredentialsClusterAddNOCCallback(app::CommandHandler * co
     // missing root. Let's early-bail with InvalidNOC.
     VerifyOrExit(failSafeContext.AddTrustedRootCertHasBeenInvoked(), nocResponse = NodeOperationalCertStatusEnum::kInvalidNOC);
 
+    // Check this explicitly before adding the fabric so we don't need to back out changes if this is an error.
+    VerifyOrExit(IsOperationalNodeId(commandData.caseAdminSubject) || IsCASEAuthTag(commandData.caseAdminSubject),
+                 nocResponse = NodeOperationalCertStatusEnum::kInvalidAdminSubject);
+
     err = fabricTable.AddNewPendingFabricWithOperationalKeystore(NOCValue, ICACValue.ValueOr(ByteSpan{}), adminVendorId,
                                                                  &newFabricIndex);
     VerifyOrExit(err == CHIP_NO_ERROR, nocResponse = ConvertToNOCResponseStatus(err));