Support AWS credential_process

[JesseStimpson]

AWS credentials file supports a configuration called credential_process that executes a program to retrieve credentials.

https://docs.aws.amazon.com/cli/v1/userguide/cli-configure-sourcing-external.html

[onno-vos-dev]

Suggested change

	CredsMap = maps:from_list(lists:filtermap(
	fun
	({<<"AccessKeyId">>, AKI}) -> {true, {<<"aws_access_key_id">>, AKI}};
	({<<"SecretAccessKey">>, SAK}) -> {true, {<<"aws_secret_access_key">>, SAK}};
	({<<"SessionToken">>, ST}) -> {true, {<<"aws_session_token">>, ST}};
	(_) -> false
	end, maps:to_list(CredResult))),
	Keys = [<<"AccessKeyId">>,<<"SecretAccessKey">>,<<"SessionToken">>],
	CredsMap = maps:filter(fun(K, V) -> lists:member(K, Keys) end, CredResult),

[onno-vos-dev]

First off, thank you for the PR! This is great! 🚀 🙏

Couple of initial comments:

• Linting fails. (You have a line too long at line 149). My suggestion should sort that out and simplify things IMHO.
• I'd really like to see a test which I'm perfectly fine in using some mecking 👍 But "something" to exercise this sort of codepath. Happy to help if you don't have time or aren't as comfortable fiddling around with our test SUITE 👍

[JesseStimpson]

Ah sorry I tried to fix the lint before I saw your message. I'll take your approach, thanks!

I'll have a go at the test as well.

[JesseStimpson]

Test added.

I wasn't able to follow your approach for the map construction. Annoyingly, the keys are different between the JSON representation from the credential_process (e.g. AccessKeyId) and the keys in the credentials file itself (e.g. aws_access_key_id)

Moreover, since SessionToken/aws_session_token is optional, I think the current code is the most succinct I can make it.

I can break it out into a separate function if you think that would help readability.

[onno-vos-dev]

Test added.

I wasn't able to follow your approach for the map construction. Annoyingly, the keys are different between the JSON representation from the credential_process (e.g. AccessKeyId) and the keys in the credentials file itself (e.g. aws_access_key_id)

Moreover, since SessionToken/aws_session_token is optional, I think the current code is the most succinct I can make it.

I can break it out into a separate function if you think that would help readability.

Ofcourse. My coffee-deprived brain didn't take that into account 😅

Looks good ❤️ I've added a few more reviewers. I'll grab a cup of coffee and take a look around lunch 👍

[onno-vos-dev]

LGTM 👌 Thank you! Will merge and tag in a couple of hours 👌