This PR makes user information from JWT tokens available as part of a Task.
Included changes:
* Renamed `verify_token` to `call_if_agent`, since this function is specific to agent token verification
* Renames `is_authorized` to `is_agent`, since this function checks if the token is an agent
* Adds support for unmanaged nodes in `is_agent` (see #133 for information)
* Saves the user information from the JWT token on task create as part of `TaskConfig`
Note, `TaskConfig` is what is provided to notification templates. This enables Github issues and ADO work items to tie back to the user that created the task.
Note, while `upn` _usually_ means email for AAD user tokens. If we were going to make use of the email address, we should perform a graph lookup based on the `oid`, but we're not.
