feat(nextauth): properly handle signout

When signing out, by default keycloak session is not terminated, this fixes it and sends a request to keycloak instance to terminate the keycloak session.

src/server/auth.ts

@@ -6,6 +6,9 @@ import {
   type DefaultSession,
 } from "next-auth";
 import KeycloakProvider from "next-auth/providers/keycloak";
+import { type KeycloakProfile } from "next-auth/providers/keycloak";
+import { type JWT } from "next-auth/jwt";
+import { type OAuthConfig } from "next-auth/providers";
 import { env } from "~/env.mjs";
 import { prisma } from "~/server/db";
 
@@ -30,6 +33,18 @@ declare module "next-auth" {
   // }
 }
 
+/**
+ * Part of the Keycloak fix/workaround, see code bellow for method `signOut`.
+ *
+ * @see https://stackoverflow.com/a/75526977
+ */
+declare module 'next-auth/jwt' {
+  interface JWT {
+    id_token?: string;
+    provider?: string;
+  }
+}
+
 /**
  * Options for NextAuth.js used to configure adapters, providers, callbacks, etc.
  *
@@ -46,6 +61,18 @@ export const authOptions: NextAuthOptions = {
         image: user.image,
       },
     }),
+    /**
+     * Part of the Keycloak fix/workaround, see code bellow for method `signOut`.
+     *
+     * @see https://stackoverflow.com/a/75526977
+     */
+    async jwt({ token, account }) {
+      if (account) {
+        token.id_token = account.id_token
+        token.provider = account.provider
+      }
+      return token
+    },
   },
   adapter: PrismaAdapter(prisma),
   providers: [
@@ -68,6 +95,22 @@ export const authOptions: NextAuthOptions = {
      * @see https://next-auth.js.org/providers/github
      */
   ],
+  events: {
+    /**
+     * Fix for Keycloak not destroying the session token on logout,
+     * we must send an extra request to delete the session.
+     *
+     * @see https://stackoverflow.com/a/75526977
+     */
+    async signOut({ token }: { token: JWT }) {
+      if (token.provider === "keycloak") {
+        const issuerUrl = (authOptions.providers.find(p => p.id === "keycloak") as OAuthConfig<KeycloakProfile>).options!.issuer!
+        const logOutUrl = new URL(`${issuerUrl}/protocol/openid-connect/logout`)
+        logOutUrl.searchParams.set("id_token_hint", token.id_token!)
+        await fetch(logOutUrl);
+      }
+    },
+  }
 };
 
 /**