Resolve "py4web: after user creation, redirection fails" + various user related fix + test_user.js cypress tests
requested to merge 5169-py4web-after-user-creation-redirection-fails into feature-s/py4web-by-default
Closes #5169 (closed) Fixed the corresponding cypress test
In the meantime, fixed small other user related issues (cf git log) + another cypress test in test_user.js.