Make global context easier to access for users

[timsaucer]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

#982 added convenience functions to use a global context for operations like read_parquet and others. It would be good to expose the global context to make it easier for users to register functions with it.

Describe the solution you'd like

• Rename _global_ctx to global_ctx.
• Add global context to python wrapper code
• Add unit tests
• Add user documentation

Describe alternatives you've considered

We can leave as is.

Additional context

It is worth considering if there are other common user functions that would benefit from the same treatment as the file readers. If so, we could open new issues for them

[Spaarsh]

Key Points:

1. | operator not supported for python < 3.10, anyone pulling the main will not be able to use SessionContext at all
2. global_ctx already exposed to python

I have left a detailed comment under #982 here

[Spaarsh]

Should make a PR that doesn't use the | operator in the read_* functions? We simply need to use the Union function instead. I already have that code running locally.

[timsaucer]

No, we have plenty of other points in the code where we us the | operator. Also, that issue is related, but not the topic of this issue. We also have a PR up that resolves the error and adds ruff checking to prevent it from happening in the future.

[timsaucer]

I understand what you mean by "global context is already exposed" but I mean that it should be treated in the wrapper functions as well so that users get a nice python interface and don't need to jump into the _internal package. I updated the issue with hopefully clearer language.

[jsai28]

take

[timsaucer]

Closed by #1060