Saving connection overwrites existing custom attributes

[MrPrashantT]

Saving a custom social connection overwrites existing custom attributes (e.g. upstream_params) that were added via API v2.

1. Create a custom social connection via the extension
2. Update Connection via API v2, with upstream_params, e.g:

{
  "options": {
   ...//existing attributes
   ...
    "upstream_params": {
      "login_options": {
        "alias": "display"
      }
    }
  }
}

3. Reload the extension. The GET /connection/{conn_id} contains the new upstream_params in the options.
4. Click Save without modifying anything. The PATCH call doesn't contain the upstream_params, hence this is lost.

Expected behaviour is for the PATCH call to preserve the existing upstream_params.