The mod_auth_oidc needs an additional directive (`OIDCXForwardedHeaders`)
in case FreshRSS is running behind a reverse proxy, so it knows what host,
protocol and port were used to access it. This information is then used
in the `redirect_uri` when directing the user agent (browser) to the identity
provider for authentication.

Please note that, if you are running FreshRSS behind a reverse proxy that
handles TLS, you may need to update your identity provider's configuration so
it accepts `https://...` as a `redirect_uri`.

…aders Apache configuration directive