FlowAuth should generate tokens on demand

[greenape]

At the moment, adding a new token does just that - it generates and stores a token. There would be some advantages to changing this, so that the current token list is a list of configured token generators, and clicking the token button generates a new one with that generator. Would also mean it would make sense to add in an edit and delete button.

(I imagine we'd still want to record somewhere the generation of tokens.)

[flowstef]

I second the delete button. The list grows quite quickly.
Also I suggest ordering by date descending instead of ascending - not sure if this should be a new issue.

[Thingus]

Will address as part of #5163