Allow multiple signing keys to be provided

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

src/integrationTest/java/org/opensearch/security/http/JwtAuthenticationWithUrlParamTests.java

@@ -72,7 +72,7 @@ public class JwtAuthenticationWithUrlParamTests {
         "jwt",
         BASIC_AUTH_DOMAIN_ORDER - 1
     ).jwtHttpAuthenticator(
-        new JwtConfigBuilder().jwtUrlParameter(TOKEN_URL_PARAM).signingKey(PUBLIC_KEY).subjectKey(CLAIM_USERNAME).rolesKey(CLAIM_ROLES)
+        new JwtConfigBuilder().jwtUrlParameter(TOKEN_URL_PARAM).signingKey(List.of(PUBLIC_KEY)).subjectKey(CLAIM_USERNAME).rolesKey(CLAIM_ROLES)
     ).backend("noop");
 
     @Rule