feat: use the signing secret instead of the verification token (joe#104)

Description

The Verification Token is deprecated, use signing secret instead.

Related issue

joe#104 (closed)

Examples

Checklist

• the MR description has been reviewed
• this MR contains text changes and they have been reviewed OR there are no texts changes
• this MR contains GUI/CLI changes and they have been reviewed OR there are no GUI/CLI changes
• this MR contains API changes and they have been reviewed OR there are no API changes