fix: broken Content-MD5 header for S3 upload

[mwbrooks]

Changelog

Fix the S3 Content-MD5 header when deploy a Deno app to Slack.

Summary

This pull request removes the MD5 hash computation and Content-MD5 header from S3 presigned POST uploads.

• Flagged by Snyk as [LOW] Use of Password Hash With Insufficient Computational Effort for using crypto/md5 in internal/api/s3_upload.go.
• The hash was also bugged - it was always 0 bytes and produced an empty content digest (1B2M2Y8AsgTpgAmY7PhCfg==) because it was hashed over an already-exhausted io.Reader.
• Content-MD5 is optional for S3 presigned POST uploads since integrity is enforced by the signed policy.
• The tests were testing for a 0 byte empty content hash (1B2M2Y8AsgTpgAmY7PhCfg==) 🤷🏻

Preview

N/A

Testing

# Create Deno app
$ slack create my-app
# -> Select Automation App -> Deno SDK

$ cd my-app/

# Deploy the app
$ slack deploy

# Test the app
# -> Copy & paste trigger in Slack

# Clean up
$ slack delete -f
$ cd ../
$ rm -rf my-app/

Requirements

• 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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.30%. Comparing base (1e9c53e) to head (e4ca14d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #527   +/-   ##
=======================================
  Coverage   71.29%   71.30%           
=======================================
  Files         222      222           
  Lines       18682    18677    -5     
=======================================
- Hits        13320    13318    -2     
+ Misses       4185     4184    -1     
+ Partials     1177     1175    -2     

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[zimeg]

@mwbrooks Amazing find! I'm glad we have tools that help us improve code health since this is not obvious to me otherwise 📸

[mwbrooks]

Thanks for the super quick review @zimeg!