feat(oauth): Add option to logout from OpenID Connect provider

* Fixes #598

Signed-off-by: Marvin A. Ruder <signed@mruder.dev>

backend/src/oauth/provider/github.provider.ts

@@ -61,6 +61,7 @@ export class GitHubProvider implements OAuthProvider<GitHubToken> {
       providerId: user.id.toString(),
       providerUsername: user.name ?? user.login,
       email,
+      idToken: `github:${token.idToken}`,
     };
   }