fix: handled spaces in variable names for crosstab (#305)

[JessUWE]

• Implemented add_backticks helper to wrap variable names containing spaces, fixing numexpr syntax errors
• Updated get_queries to apply backticks to row and column identifiers
• Removed obsolete string manipulation in crosstab_with_totals

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.92%. Comparing base (df8b3b7) to head (deab03e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #321      +/-   ##
==========================================
+ Coverage   99.76%   99.92%   +0.16%     
==========================================
  Files           9        9              
  Lines        1253     1269      +16     
==========================================
+ Hits         1250     1268      +18     
+ Misses          3        1       -2     

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[rpreen]

Do we need a unit test to confirm this works and make sure nobody breaks it in the future?

It would be nice to have type hints in all the functions to help readability and help confirm behaviour with mypy, but I see lots of them missing all over the code base (not just here) - @jim-smith that might be a good first task for someone - along with lots of refactoring and test improvements?

[jim-smith]

@rpreen @JessUWE :

1. Yes there should be a unit test for this (not a fan of pragma: nocoverage) -- but it looks like there is one so why do we need the pragma?
2. Yes to adding typehints being a good job for an intern if we can get the right one

[jim-smith]

@JessUWE I've approve and merged in the PR that provides a test for the rounded_survival_table()
so you might want other merge the updated main back into this branch before you add the new test for cross tab() with variables that have spaces in?

[jim-smith]

@JessUWE but the rest of the code is a sensible and better refactored handling of the issue this PR addresses