fix(auth): stuck on page after email verification

fix(auth): stuck on page after email verification

closes opentalk/bugs#14

Explanation

Problem was, what we came directly from keycloak to the webapp and had no change to create the code_verifier, now we check if the code_verifier exists and if not, we do a normal signIn-Roundtrip again.

QA

1. activate user registration in keycloak
2. activate email verification in keycloak
3. register a new user
4. validate email
5. click on the link in the validation email
6. check if dashboard is opened and the app gets not stuck into a blankscreen

local testing

• start locally testing environment with profiles backend and mailer
• configure keycloak for sending emails
• look QA steps