Authentication updates

I didn't see !606 (closed), sorry!

This change is a little more wide-ranging, but I can pull out just the core. I've done a few things:

1. remove scopes from the tokens
2. attempt to figure out if the AP expects the igwn or scitoken
3. update how we specify the datafind server to use GWDATAFIND_SERVER when appropriate
4. allow generation jobs to run in the IGWN pool, currently they're hardcoded to run in the local pool
5. add support for submitting to the local pool from an OSG AP

I think we definitely need 1.

2, we may be better off having this specified via the config file (maybe defaulting to the current behaviour) so that people don't have to submit from the node they set up the dag on.

For some reason using datafind.igwn.org started failing for me for O4 data, so I put this in to fix that. I think it's generally useful, but should probably be moved to a different MR.

The fourth and fifth points are things I've been thinking about for a while and didn't really mean to commit on this branch.

@james-clark would you be able to look at these proposed changes, especially this file?

EDIT I added another argument to the parser to allow overwriting the issuer method, for example if I want to run bilby_pipe for a bunch of things on one AP and then submit from different ones, this will allow that. I had this come up in testing, so I don't think it's too tortured a possibility.

Closes #304 (closed)