Attempt to vendor the stand-alone bson package to prevent conflicts with pymongo

[cnweaver]

Description

This attempts to fix #248 while keeping large message offload support working by default.

Checklist

• All new functions and classes are documented and adhere to Google doc style (3.8.3-3.8.6 of this document)
• Add/update sphinx documentation with any relevant changes.
• Add/update pytest-style tests in /tests, ensuring sufficient code coverage.
• make test runs without errors.
• make lint doesn't give any warnings.
• make format doesn't give any code formatting suggestions.
• make doc runs without errors and generated docs render correctly.
• Check that CI pipeline run on this PR passes all stages.
• Review signoff by at least one developer.

NOTE: If this PR relates to a release, open and reference an issue with the Release checklist template.

[cnweaver]

Tests generally work, but the linter is failing.
Making sure that all licensing terms are met (particularly when packaging) still needs to be done.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.76%. Comparing base (98590a4) to head (51023d6).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #250   +/-   ##
=======================================
  Coverage   99.76%   99.76%           
=======================================
  Files          16       16           
  Lines        2126     2126           
=======================================
  Hits         2121     2121           
  Misses          5        5           

Flag	Coverage Δ
pytest	99.76% <100.00%> (ø)

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[jnation3406]

I'm not up to speed on what the core issue was, but it seems like pymongo packages a bson implementation within it and installs it separately as bson, but its really a modified version of bson and not what you have copied here and wanted installed? Is the main problem that users of hop client that already have mongodb installed break their pymongo when installing hop-client since it installs the base bson over the already installed customized mongodb bson? It looks like its using a c implementation for a some of the bson stuff in pymongo here... Would it work to just depend on pymongo (which contains bson) rather than bson in the hop-client? It seems like the internal pymongo bson codec might be more efficient anyway since it uses c.

[cnweaver]

#248 describes the original problem pretty succintly, which is that if hop-client is installed (it need not even be imported), pymongo is broken and cannot be imported.
As best I can tell the 'bson' installed by pymongo is probably the original in the python space, but it is handled in an awkward way (which is the cause of our problem), and it is as you note a C extension, which requires per-target wheels. The bson package, copied here, is a lighter-weight, pure python implementation which may not be as performant, but has been adequate for our needs (which are pretty minimal), and keeps our code architecture-independent.
I think we don't really want to add a pymongo dependency since we 1) don't really use it and 2) it makes a mess that I'd rather not spread that to affect more people who don't expect it. It would have been nice to optionally use the pymongo version if it is already installed, but pyproject.toml is, as far as I can tell (and not unreasably), not expressive enough to make a dependency conditional on other packages not being present in the installation environment.

[adambrazier]

Looks good to me (inasmuch as I understand pyproject.toml)