Resolves https://github.com/go-vikunja/frontend/issues/109
Vikunja would save the api url with `http` instead of `https` when the frontend was accessed via https. This was fine in most cases when the server would redirect all requests made to http to the secure https variant. However, in newer Firefox versions (and soon, Chrome probably as well) the browser would not follow that redirect anymore. Hence, we need to make sure to only make api requests to the same protocol. Doing API requests from an https hosted fronted to an http hosted api would probably fail already anyway.
Co-authored-by: kolaente <k@knt.li>
Reviewed-on: #3303
Reviewed-by: Dominik Pschenitschni <dpschen@noreply.kolaente.de>
Co-authored-by: konrad <k@knt.li>
Co-committed-by: konrad <k@knt.li>
