refactor: Simplify jwksRsa import and enhance username extraction logic in JwtAuthGuard

src/modules/auth/auth.service.ts

@@ -1,11 +1,11 @@
 import { Injectable, UnauthorizedException } from "@nestjs/common";
 import { ConfigService } from "@nestjs/config";
 import * as jwt from "jsonwebtoken";
-import JwksRsa, * as jwksRsa from "jwks-rsa";
+import * as jwksRsa from "jwks-rsa";
 
 @Injectable()
 export class AuthService {
-	private jwksClient: JwksRsa.JwksClient;
+	private jwksClient: jwksRsa.JwksClient;
 
 	constructor(configService: ConfigService) {
 		this.jwksClient = jwksRsa({

src/modules/auth/guards/jwt.guard.ts

@@ -30,7 +30,9 @@ export class JwtAuthGuard implements CanActivate {
 			let user = await this.userService.findOrCreate({
 				id: jwtPayload.sub.toString(),
 				username:
-					jwtPayload[this.configService.get("auth.usernameField")],
+					jwtPayload[this.configService.get("auth.usernameField")] || 
+					jwtPayload["preferred_username"] || 
+					jwtPayload["email"],
 			});
 
 			request.user = user;