fix(acme): correctly concat returned error (#11364)

In the last change we added string concatenation the wrong way leading to empty logs. This addresses the problem

CHANGELOG.md

@@ -132,6 +132,8 @@
   [#10559](https://github.com/Kong/kong/pull/10559)
 - **Zipkin**: Fixed an issue that traces not being generated correctly when instrumentations are enabled.
   [#10983](https://github.com/Kong/kong/pull/10983)
+- **Acme**: Fixed string concatenation on cert renewal errors
+  [#11364](https://github.com/Kong/kong/pull/11364)
 
 #### PDK
 

kong/plugins/acme/client.lua

@@ -163,7 +163,8 @@ local function order(acme_client, host, key, cert_type, rsa_key_size)
 
   local cert, err = acme_client:order_certificate(key, host)
   if err then
-    return nil, nil, "could not create certificate for host: ", host, " err: " .. err
+    local concatErr =  "could not create certificate for host: " .. host .. " err: " .. err
+    return nil, nil, concatErr
   end
 
   return cert, key, nil