204: Handle proxies when using Slack WebClient

[raihle]

Summary

• Resolves Proxy configuration is ignored when using bot token #204

Requirements (place an x in each [ ])

The CLA mentioned in the Contributing Guidelines could not be found, but I'm (probably) willing to sign it if you can point me in the right direction. The bot took care of that promptly!

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @raihle to sign the Salesforce Inc. Contributor License Agreement.

[hello-ashleyintech]

Hi, @raihle! Thanks so much for opening this PR 🙌 This is looking good so far! I'm going to run the integration tests on my end to make sure all looks good, but it's a great sign that the unit tests are passing, especially with the updates to slack-send!

At first glance the two use cases you provided for the web client test make sense. I have to get access to a particular workspace to run the integration tests, so I'll drop in an update once I'm able to run these with the results as well as if I have any additional thoughts on the test cases! 👍

[hello-ashleyintech]

@raihle Great news - this is looking good on my end and I have confirmed through #206 that the integration tests pass!

This PR is currently failing the payload integration test due to a non-related issue that was uncovered where that test is having trouble parsing certain characters when they're in the body of a PR. I have a fix for that in #207. Waiting for approval for that one, and then once that has been merged in and the integration test is updated, I'll approve and merge this one in as well. Also - I have left one small comment on testing that I would like to get your thoughts on before approving and merging, so let me know if there are any questions there! 😄

[filmaj]

LGTM but let's also document the ability to use https_proxy and HTTPS_PROXY environment variables in the README.

[hello-ashleyintech]

Confirmed integration tests for this code are passing in #206 and documentation for the HTTPS_PROXY env var has been added. This is looking great to me, so I'll approve and merge this - thanks so much for your contribution, @raihle! 🙇

[raihle]

@filmaj Good call, I added a new section (sibling to the techniques) with an example using HTTPS_PROXY.

[filmaj]

Thank you so much for your contribution!