Allow multiple signing keys to be provided

Signed-off-by: Stephen Crawford <[email protected]>

src/main/java/com/amazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java

@@ -129,7 +129,7 @@ public AuthCredentials run() {
     }
 
     private AuthCredentials extractCredentials0(final SecurityRequest request) {
-        if (jwtParsers.isEmpty() || jwtParsers.getFirst() == null) {
+        if (jwtParsers.isEmpty() || jwtParsers.get(0) == null) {
             log.error("Missing Signing Key. JWT authentication will not work");
             return null;
         }