Make classes final

Author: rmichela

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XForwardedClientCert.java

@@ -18,7 +18,7 @@
  * x-forwarded-client-cert (XFCC) is a proxy header which indicates certificate information of part or all of the
  * clients or proxies that a request has flowed through, on its way from the client to the server.
  */
-public class XForwardedClientCert {
+public final class XForwardedClientCert {
     /**
      * The metadata key used to access any present {@link XForwardedClientCert} objects.
      */

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XfccMarshaller.java

@@ -19,7 +19,7 @@
  * @see <a href="https://www.envoyproxy.io/docs/envoy/latest/configuration/http_conn_man/headers.html#config-http-conn-man-headers-x-forwarded-client-cert">Envoy XFCC Header</a>
  * @see <a href="https://github.com/linkerd/linkerd/issues/1153">Linkerd XFCC Header</a>
  */
-public class XfccMarshaller implements Metadata.AsciiMarshaller<List<XForwardedClientCert>> {
+public final class XfccMarshaller implements Metadata.AsciiMarshaller<List<XForwardedClientCert>> {
     @Override
     public String toAsciiString(List<XForwardedClientCert> value) {
         return value.stream().map(XForwardedClientCert::toString).collect(Collectors.joining(","));

grpc-contrib/src/main/java/com/salesforce/grpc/contrib/xfcc/XfccServerInterceptor.java

@@ -20,7 +20,7 @@
  * @see <a href="https://www.envoyproxy.io/docs/envoy/latest/configuration/http_conn_man/headers.html#config-http-conn-man-headers-x-forwarded-client-cert">Envoy XFCC Header</a>
  * @see <a href="https://github.com/linkerd/linkerd/issues/1153">Linkerd XFCC Header</a>
  */
-public class XfccServerInterceptor implements ServerInterceptor {
+public final class XfccServerInterceptor implements ServerInterceptor {
     private static final Metadata.Key<List<XForwardedClientCert>> XFCC_METADATA_KEY = Metadata.Key.of("x-forwarded-client-cert", new XfccMarshaller());
 
     @Override