Restore ability to specify token secret for API token (#800)

[BruceMacD]

When standing up Infra it is possible to specify what the API tokens for connecting destinations and root access are as code. This requires creating/updating an API token and its associated access token.

If a token has an empty key or secret then they are generated in the token creation logic not changed by this PR.

• Wrote appropriate unit tests
• Considered security implications of the change
• Updated associated docs where necessary
• Updated associated configuration where necessary
• Change is backwards compatible if it needs to be (user can upgrade without manual steps?)
• Nothing sensitive logged

Resolves #800

[ssoroka]

Can we avoid passing around the empty objects by instead splitting this into two functions? This behavior exists for the CreateOrUpdate function (which is probably going away?), and it sort of muddies the implementation of the non-create-or-update version. If the client had to do all this create-or-update functionality on the client-side, it seems like this workflow would break anyway.

[BruceMacD]

Can we avoid passing around the empty objects by instead splitting this into two functions? This behavior exists for the CreateOrUpdate function (which is probably going away?), and it sort of muddies the implementation of the non-create-or-update version. If the client had to do all this create-or-update functionality on the client-side, it seems like this workflow would break anyway.

Good call @ssoroka, I'll update with this suggestion.

[jmorganca]

LGTM - thanks for fixing this 💯