Fix: encode body before signing to match manticore adapter encoding.

[dblock]

Description

Manticore adapter encodes the request body before sending in a different way than the ruby code before signing. In the case of a ISO-8859-1 string it may not match the body being signed, causing a 403.

With

puts "       encoding: #{minimum_encoding_for(params[:body])}"
puts "  ruby encoding: #{params[:body].encode(minimum_encoding_for(params[:body])).inspect}"
puts "apache encoding: #{EntityUtils.toString(StringEntity.new(params[:body], minimum_encoding_for(params[:body]))).inspect}"

       encoding: UTF-8
  ruby encoding: "{\"index\":{\"_id\":null,\"_index\":\"my-index\",\"routing\":null}}\n{\"message\":\"bo\xEEte de r\xE9ception\",\"@version\":\"1\",\"@timestamp\":\"2023-08-23T12:21:54.057Z\"}\n"
apache encoding: "{\"index\":{\"_id\":null,\"_index\":\"my-index\",\"routing\":null}}\n{\"message\":\"bo�te de r�ception\",\"@version\":\"1\",\"@timestamp\":\"2023-08-23T12:21:54.057Z\"}\n"

I attempted to match encoding in pure ruby, too, but couldn't find the magical combination. It would be nice if Manticore had a way to callback with the entity being sent to avoid encoding twice, too :(

Repro in #207 (comment).

Issues Resolved

Closes #207.

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has documentation added
• Commits are signed as per the DCO using --signoff

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[dlvenable]

Thanks for finding the cause of this issue!

[kffallis]

appreciate the work on this team

[opensearch-trigger-bot]

The backport to 1.3 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.3 1.3
# Navigate to the new working tree
cd .worktrees/backport-1.3
# Create a new branch
git switch --create backport/backport-217-to-1.3
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 ada13fa1303a9868c12e7ef69298e3c72fff59d4
# Push it to GitHub
git push --set-upstream origin backport/backport-217-to-1.3
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.3

Then, create a pull request where the base branch is 1.3 and the compare/head branch is backport/backport-217-to-1.3.