kafka: fixed: find tran coordinator was not ACL verified

The code to handle FindCoordinator request for transaction coordinator type
appeared before the caller is checked for authorization for this operation
against the ACL. Now the chech has been moved before any other handling.

src/v/kafka/server/handlers/find_coordinator.cc

@@ -72,6 +72,21 @@ ss::future<response_ptr> find_coordinator_handler::handle(
     find_coordinator_request request;
     request.decode(ctx.reader(), ctx.header().version);
 
+    if (request.data.key_type == coordinator_type::group) {
+        if (!ctx.authorized(
+              security::acl_operation::describe, group_id(request.data.key))) {
+            return ctx.respond(find_coordinator_response(
+              error_code::group_authorization_failed));
+        }
+    } else if (request.data.key_type == coordinator_type::transaction) {
+        if (!ctx.authorized(
+              security::acl_operation::describe,
+              transactional_id(request.data.key))) {
+            return ctx.respond(find_coordinator_response(
+              error_code::transactional_id_authorization_failed));
+        }
+    }
+
     if (request.data.key_type == coordinator_type::transaction) {
         if (!ctx.are_transactions_enabled()) {
             return ctx.respond(
@@ -98,21 +113,6 @@ ss::future<response_ptr> find_coordinator_handler::handle(
           find_coordinator_response(error_code::unsupported_version));
     }
 
-    if (request.data.key_type == coordinator_type::group) {
-        if (!ctx.authorized(
-              security::acl_operation::describe, group_id(request.data.key))) {
-            return ctx.respond(find_coordinator_response(
-              error_code::group_authorization_failed));
-        }
-    } else if (request.data.key_type == coordinator_type::transaction) {
-        if (!ctx.authorized(
-              security::acl_operation::describe,
-              transactional_id(request.data.key))) {
-            return ctx.respond(find_coordinator_response(
-              error_code::transactional_id_authorization_failed));
-        }
-    }
-
     return ss::do_with(
       std::move(ctx),
       [request = std::move(request)](request_context& ctx) mutable {