Integrate NextAuth with Keycloak and implement JWT validation in internal_frontend.

internal_frontend/types/auth.d.ts

@@ -0,0 +1,16 @@
+import NextAuth from "next-auth";
+import {JWT} from "next-auth/jwt";
+
+declare module "next-auth/jwt" {
+    interface JWT {
+        access_token?: string;
+        refresh_token?: string;
+    }
+}
+
+declare module "next-auth" {
+    interface Session {
+        accessToken?: string;
+        refreshToken?: string;
+    }
+}