fix: Post Login URL integrated

[janldeboer]

Fixing post login redirect behaviour

Description

I integrated the ZITADEL_POST_LOGIN_URL to work as expected and described in .env.example:

# The internal URL within your application where users are sent after a
# successful login is processed at the callback URL.
# Defaults to "/profile" if not specified.
ZITADEL_POST_LOGIN_URL="/profile"

Related Issue

I worked on #18 while stumbling across this little mistake.

Motivation and Context

Restoring expected / planned behaviour

How Has This Been Tested?

I manually tested:

• Commenting out the ZITADEL_POST_LOGIN_URL in my .env file -> redirects to /profile after login
• Setting /profile and /test as post login url -> redirects to those after login

Documentation:

None needed

Checklist:

• I have updated the documentation accordingly.
• I have assigned the correct milestone or created one if non-existent.
• I have correctly labeled this pull request.
• I have linked the corresponding issue in this description.
• I have requested a review from at least 2 reviewers
• I have checked the base branch of this pull request
• I have checked my code for any possible security vulnerabilities