Fix premature log entry

[johanib]

Prior to this change, a authentication_result FAILED appeared in the logs, even though the authentication was a success.

This change fixes that by logging after the markSecondFactorVerified call, resulting in authentication_result OK.

Fixes #433

[MKodde]

Hip hip hurray:

The authentication log message now states:

{
    "message": "Second Factor Authenticated",
    "context": {
        "second_factor_id": "72c60efe-94a5-48b9-9da8-c7d0113121d1",
        "second_factor_type": "demo_gssp",
        "institution": "dev.openconext.local",
        "authentication_result": "OK",
        "resulting_loa": "http://dev.openconext.local/assurance/loa3",
        "sso": "NO",
        "identity_id": "urn:collab:person:dev.openconext.local:admin",
        "authenticating_idp": null,
        "requesting_sp": "https://selfservice.dev.openconext.local/authentication/metadata",
        "datetime": "2025-12-18T14:55:27+01:00",
        "sari": "_e9522e1e16f8f663ca6b83eeb3871a15d73ec83a6cef267b0b2a82a7c7f5"
    },
    "level": 250,
    "level_name": "NOTICE",
    "channel": "security",
    "datetime": "2025-12-18T14:55:28+01:00",
    "extra": {
        "server": "gateway.dev.openconext.local",
        "application": "stepup-gateway",
        "request_id": "08efebde281de4fe75f9844a0dd48cc1"
    }
}