Support script-based mechanism to obtain a RT

[paulmillar]

I'm working on an interoperability with a large infrastructure.

They are (by and large) support using OIDC to obtain an AT from a RT following the OIDC standard. However, the process for obtaining the RT is non-standard.

I have written a script that obtains the RT automatically.

Within this script, I could run oidc-gen to create an account with this RT, using this --rt option. (I don't, but I could).

This is OK, but this doesn't take into account that the RT can (and does) expire.

If oidc agent account were to know about this script then it could call the script automatically when the RT expires.

So, I'm thinking it would be useful if an oidc-agent account could be configured to call out to a script that fetches the RT "on demand".