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/discord.provider.ts

@@ -91,6 +91,7 @@ export class DiscordProvider implements OAuthProvider<DiscordToken> {
       providerId: user.id,
       providerUsername: user.global_name ?? user.username,
       email: user.email,
+      idToken: `discord:${token.idToken}`,
     };
   }
 

backend/src/oauth/provider/genericOidc.provider.ts

@@ -197,6 +197,7 @@ export abstract class GenericOidcProvider implements OAuthProvider<OidcToken> {
       providerId: idTokenData.sub,
       providerUsername: username,
       ...(isAdmin !== undefined && { isAdmin }),
+      idToken: `${this.name}:${token.idToken}`,
     };
   }
 
@@ -251,6 +252,8 @@ export interface OidcConfiguration {
   id_token_signing_alg_values_supported: string[];
   scopes_supported?: string[];
   claims_supported?: string[];
+  frontchannel_logout_supported?: boolean;
+  end_session_endpoint?: string;
 }
 
 export interface OidcJwk {

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}`,
     };
   }