Tracking issue for release of DF 42

[timsaucer]

Tracking issue for release of DF 42. Please let us know if there's a particular issue you're waiting on!

PRs under review:

• fix: Calling count on a pyarrow dataset results in an error #843
• build(deps): upgrade setup-protoc action and protoc version number #873
• Fix regression on register_udaf #878

Issues to be resolved and included in release:

• Bindings to datafusion-proto #869
• Add support for user defined window functions #845
• Docs: Running unit-tests against a release candidate #804
• Bump maturin version to satisfy conda-forge constraints? #701
• Enhance udf to take additional non-expr arguments #822

[timsaucer]

@Michael-J-Ward should we try to address #701 ?

[Michael-J-Ward]

Add it in.

I upgraded the maturin version here: #725. And that has allowed the rest of the datafusion-python versions to build for conda-forge.

The last remaining conda-forge PR mentioned in #701 is conda-forge/datafusion-feedstock#46, which - from what I can tell - is blocked by something other than the maturin issue.