Allow generate key to access certain createfile traits

index.js

@@ -144,7 +144,7 @@ class S3Adapter {
     let key_without_prefix = filename;
     if (this._generateKey instanceof Function) {
       try {
-        key_without_prefix = this._generateKey(filename);
+        key_without_prefix = this._generateKey(filename, contentType, options);
       }catch(e){
         throw new Error(e); // throw error if generateKey function fails
       }