Add automated release workflows

[willarmiros]

Which problem is this PR solving?

• Resolves Improve Release Automation #345

Short description of the changes

• Adds 2 GitHub workflows: 1 that automatically creates a release PR, and another that publishes all packages to NPM and cuts a GH release when that PR is merged. Most details are in Improve Release Automation #345, the only still unresolved matter is whether or not to create a draft release so you can judge for yourself after seeing the video.
• You can see my runs of identical workflows on a test repo meant to simulate this repo here, and an example of an auto-generated release PR here. I'll also be posting a video of the whole process.

[codecov]

Codecov Report

Merging #366 (a5ff1bb) into main (92656a3) will not change coverage.
The diff coverage is n/a.

❗ Current head a5ff1bb differs from pull request most recent head d9d57ba. Consider uploading reports for the commit d9d57ba to get more accurate results

@@           Coverage Diff           @@
##             main     #366   +/-   ##
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  Coverage   94.43%   94.43%           
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  Files          11       11           
  Lines         431      431           
  Branches       48       48           
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  Hits          407      407           
  Misses         24       24           

[willarmiros]

Darn, well I'm no good at video editing so it's too big to embed here on GitHub, but you can download the recording of the flow here: https://demo-video-otel-js-9y182zqovhunxlwv.s3-us-west-2.amazonaws.com/Screen+Recording+2021-02-25+at+8.45.39+PM.mov

Also, I'll be out next week. Unfortunate timing, but I'll likely be unresponsive til around 3/7.

[willarmiros]

@dyladan can you all take a look when you get a chance? I'm back from my vacation and will be able to address any comments.

[willarmiros]

@dyladan any chance for a review?

[vmarchaud]

overall LGTM, though i have a question about permission: who can launch the release workflow from github ? People with write access or do it need admin permission on the repo ?

[willarmiros]

overall LGTM, though i have a question about permission: who can launch the release workflow from github ? People with write access or do it need admin permission on the repo ?

@vmarchaud Anyone with write access can run it, but the manually-runnable workflow only creates the release PR. The PR still needs to be approved before merging, which actually triggers the publishing. So someone with write access could spam PRs (and hopefully get their write access revoked) but not actually release anything to the wild.

[dyladan]

Apologize for late review. I was on vacation all last week

[dyladan]

@obecny since this is fairly important I think we should have approval from all maintainers before merging