feat: Add the ability to use a web identity token file

[nesta219]

Issue #, if available: :

#124

Description of changes:

I would like to be able to use a github action to consume a web identity token file on an EKS worker node. I have a self-hosted runner which does not run as root and thus it does not automatically get IRSA credentials, so my current workaround is to use a bash script which handles the assume role portions, but it doesn't neatly export the credentials the way this workflow does. This pull request would allow users of this workflow to consume the web identity token file when assuming a role in a much cleaner fashion.

[paragbhingre]

@nesta219 Thank you for contributing this feature. We will take a look at it and get back to you soon.

[allisaurus]

Thanks for this contribution, @nesta219 !

Aside from light documentation feedback, I'm hoping you can add error handle re: missing files, and also wondering if you can provide some evidence of fully testing the change?

NOTE: If you're not familiar with how to run actions from a fork, it should just take running npm package, pushing the result to your fork as a new commit, and pointing your actions workflow at nesta219/configure-aws-credentials@master (but I'd suggest doing this in a branch other than the one associated with this PR, since our merge automation will attempt to generate the dist for you once it's approved)

[nesta219]

Very reasonable suggestions, I will update the docs and I'll test using the action from my fork on a real EKS node as well

[nesta219]

@allisaurus updated based on your feedback, and I also tested this with a real self-hosted github actions runner in EKS and was able to assume the web identity role using the token file

[nesta219]

[nesta219]

Note in the screen shot that the decisions to use role-duration-seconds: 3600 and role-skip-session-tagging: true were made because of some restrictions that our runner role has, and are not related to the actual GH action itself

[nesta219]

One further comment:
The nodejs assumeRoleWithWebIdentity function doesn't support the Tags parameter (the tags come from the JWT stored in the web identity token file as opposed to the request body). If you try to pass Tags, it will error with Unexpected key 'Tags' found in params, so I adjusted the logic to exclude this parameter from the request if we are using a web identity token file.

[allisaurus]

Nice catch re: tags and thanks very much for the testing @nesta219 !
I have one comment re: rearranging the logic for removing/logging the lack of tags, but overall this looks great and I'm excited to get it in.

[allisaurus]

Changes LGTM! Thanks again for working on this @nesta219