[FEAT] Role assignment in Activate instead of Register

[aspirio187]

Is your feature request related to a problem? Please describe.

When a User is created, its email address is not confirmed and the account is inactive. The role assignment should then move to the
/activate endpoint and not the /register endpoint

Describe the solution you'd like

Move the GUEST role assignment to /activate

Describe alternatives you've considered

Rename /activate to /verify-email

Additional context

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