Add exception metadata for disabled features

This change adds a new exception with consistent metadata for when
security features are not enabled. This allows clients to be able to
tell that an API failed due to a configuration option, and respond
accordingly.

Relates: kibana#55255
Resolves: elastic#52311

Author: tvernum

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/ApiKeyService.java

@@ -69,6 +69,8 @@
 import org.elasticsearch.xpack.core.security.authc.support.Hasher;
 import org.elasticsearch.xpack.core.security.authz.RoleDescriptor;
 import org.elasticsearch.xpack.core.security.user.User;
+import org.elasticsearch.xpack.security.support.FeatureNotEnabledException;
+import org.elasticsearch.xpack.security.support.FeatureNotEnabledException.Feature;
 import org.elasticsearch.xpack.security.support.SecurityIndexManager;
 
 import javax.crypto.SecretKeyFactory;
@@ -577,7 +579,7 @@ private void ensureEnabled() {
             throw LicenseUtils.newComplianceException("api keys");
         }
         if (enabled == false) {
-            throw new IllegalStateException("api keys are not enabled");
+            throw new FeatureNotEnabledException(Feature.API_KEY_SERVICE, "api keys are not enabled");
         }
     }