Gitea
- Create a new application: 
https://< your gitea host >/user/settings/applications - Under 
Redirect URIenter the correct URL i.e.https://<proxied host>/oauth2/callback - Note the Client ID and Client Secret.
 - Pass the following options to the proxy:
 
    --provider="github"
    --redirect-url="https://<proxied host>/oauth2/callback"
    --provider-display-name="Gitea"
    --client-id="< client_id as generated by Gitea >"
    --client-secret="< client_secret as generated by Gitea >"
    --login-url="https://< your gitea host >/login/oauth/authorize"
    --redeem-url="https://< your gitea host >/login/oauth/access_token"
    --validate-url="https://< your gitea host >/api/v1/user/emails"