OIDC does not use email claim for new accounts

A user created in Docspell through an OIDC login does not get an email address, even though the JWT includes the email:

```
{
[…]
"docspell_collective": "ACME",
"email": "martin.krafft@example.org",
"email_verified": true,
"name": "Martin Krafft",
"given_name": "Martin Krafft",
"preferred_username": "Martin.Krafft",
"nickname": "Martin.Krafft",
[…]
}
```

Especially if `email_verified` is true, the `email` field should be used for the new user.