duckdb transformer

[cmungall]

Provides:

• compilation of transforms to duckdb-flavored SQL SELECT transforms using SQLCompiler
• an alternative to object_transformer that bypasses in-memory by using duckdb (unless :in-memory: is specified of course)

Currently this mixes duckdb specific logic with sql. We will likely want to make heavy use of lists, structs, etc, bypassing the normal relmodel_transformer in linkml, so it will likely make sense to split the logic from generic sql, with subtypes or hooks for pure relational vs duckdb vs intermediates (e.g pg)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 76.77419% with 36 lines in your changes are missing coverage. Please review.

Project coverage is 83.53%. Comparing base (71c91ff) to head (238d383).

Files	Patch %	Lines
...nkml_transformer/transformer/duckdb_transformer.py	43.33%	17 Missing ⚠️
src/linkml_transformer/session.py	72.09%	12 Missing ⚠️
src/linkml_transformer/compiler/sql_compiler.py	91.17%	6 Missing ⚠️
src/linkml_transformer/transformer/transformer.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #20      +/-   ##
==========================================
+ Coverage   80.45%   83.53%   +3.08%     
==========================================
  Files          29       29              
  Lines        1591     1701     +110     
==========================================
+ Hits         1280     1421     +141     
+ Misses        311      280      -31     

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