* Authentication: required
* Params:
* `metadata`: metadata to replace the old one
+ * `license`: Pack license
+ * `homepage`: Pack home page url
+ * `description`: Pack description
+ * `fallback-src`: Fallback url to download pack from
+ * `fallback-src-sha256`: SHA256 encoded for fallback pack archive
+ * `share-files`: is pack allowed for sharing (boolean)
* Response: JSON, updated "metadata" section of the pack and 200 status or 400 if there was a
problem with the new metadata (the error is specified in the "error" part of the response JSON)