feat: Adds check to ensure org doesn't have any outside collaborator

[farhan]

Adds check to ensure org doesn't have any outside collaborator

Ticket: openedx/public-engineering#169

Git api used to add check:
https://docs.github.com/en/rest/orgs/outside-collaborators?apiVersion=2022-11-28

Use following command to test:

repo_checks \
--org $ORGANIZATION \
--repo $REPO

[feanil]

I think putting the org_checks in the repo_checks.py executable may not be the best choice. It leads to a couple of different issues:

• The name of the script is now misleading which can lead to future confusion.
• We're losing out on some of the mechanisms we've built to control which checks get run in the current iteration. eg. We have no way to say don't run the org checks or just run a specific org check. We could fix this in place but I think that's going to make the code messier and harder to read.

A note on outside collaborators;

• Orgs can have outside collaborators, but repos can also have outside collaborators
  which are not listed at the org level. So you'll need a repo check for collaborators...Thinking a bit more about it, I think you don't need to have an org level check for this because that's pretty easy for us to review on the org itself. So maybe just focus on the repo level check?

Other notes as I'm reviewing this:

• I think it's useful pull things out into functions when things become re-usable but otherwise jumping to a function just to continue reading the code and then jumping back is not valuable in my mind. I tend to not have too many functions unless there is a clear reason to split out the code to make it easier to test or to re-use a bit of code multiple times. This is my opinion so not strictly a request to remove all functions you've split out main() but to re-assess what their usefulness is and if we can achieve some of the same readability by adding comments instead.

[farhan]

@feanil Thanks for flagging the concern

I initially thought api is not returning the list of outside collaborators as no relevant data is available in the response but we can add filter. So task is done in a simple way.

[feanil]

Looks great!