Update to JWT v5 to fix vulnerability

[matthiasthomas]

The current version uses github.com/golang-jwt/jwt v3.2.2+incompatible which has a vulnerability (GO-2025-3553) related to excessive memory allocation during header parsing.

We should update to github.com/golang-jwt/jwt/v5 which fixes this vulnerability.

This affects the following files in the generates package:

• jwt_access.go
• jwt_access_test.go

The changes required are:

1. Update the import path to github.com/golang-jwt/jwt/v5
2. Update the code to use the new JWT v5 API
3. Update tests to use the new JWT v5 API

I'll submit a PR with these changes.

[matthiasthomas]

will open a PR instead