How to extend the generic oidc auth url?

I use auth0 as oidc provider. Auth0 offers the option to append query parameters to the url. In my case I want to specify the connection parameter. Apparently this option is not supported today.
Today, the url is incorrectly composed, making the query parameters invalid.

auth url example:

This results in the following request:

Does anyone have an idea how I can solve this or is such a function planned ?