[r] Add functions for setting/getting global context

[jp-dark]

Add a method for setting the global context and one for getting the global context. Use the one to get the global context in internal context helper function.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.40%. Comparing base (2b4b2b9) to head (090d452).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4364      +/-   ##
==========================================
- Coverage   86.62%   85.40%   -1.23%     
==========================================
  Files         139       77      -62     
  Lines       20955    13809    -7146     
  Branches       15       15              
==========================================
- Hits        18152    11793    -6359     
+ Misses       2803     2016     -787     

Flag	Coverage Δ
python	?
r	85.40% <100.00%> (+0.04%)	⬆️

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Components	Coverage Δ
python_api	∅ <ø> (∅)
libtiledbsoma	77.24% <ø> (ø)

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[aaronwolen]

Thanks! Great documentation and user messaging.

There seems to be a lot of overlap between the getter/setter's functionality. It looks like both functions:

• Check if a context exists
• Create one if needed
• Store it in .pkgenv[["somactx"]]
• Return the context

So the only differences are:

• set_default_context() accepts config and always creates a new one
• get_default_context() has no args and only creates one if missing

I'd expect get_default_context() to error if one wasn't set and suggest users call set_default_context(). That might make the use case for each function clearer.

And then for internal use within get_soma_context() maybe we add an internal helper .get_or_create_default_context() that matches the current behavior of get_default_context() so factory functions automatically handle lazy creation for users.