Ability to export and import authentication tokens

__Proposal:__
Ability to export and import authentication tokens

__Current behavior:__
Currently it is not possible to generate "custom" tokens. Tokens are always random.

__Desired behavior:__
Ability to create custom tokens or to export and import tokens.

__Use case:__
If there is a need to move the database to another machine, all read/write devices will stop working, because there is no way to export tokens.

Start by reviewing the issue's proposal for custom tokens and token export/import, focusing on the database-migration use case. Define the supported token behavior and migration expectations before implementation; done means read/write devices continue working after the database moves to another machine.

Written by the indexing model from the issue text.