Bugfix: Dataframe transformation

[anthonylasso]

Description

This PR adds a new field source_text to the DFTransformation proto and propagates it throughout the backend. The source_text value is stored in a new table called source_variant_text. This fixes an issue where the dashboard would display a binary string.

Now users can correctly read the transformation function.

Request for Comment

before

after

source_variant_text table

Type of change

Does this correspond to an open issue?

Select type(s) of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have fixed any merge conflicts

[codecov]

Codecov Report

Merging #926 (7eadb57) into main (2bd119f) will decrease coverage by 2.13%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #926      +/-   ##
==========================================
- Coverage   57.18%   55.05%   -2.13%     
==========================================
  Files          72       72              
  Lines       14153    14158       +5     
==========================================
- Hits         8093     7795     -298     
- Misses       5249     5605     +356     
+ Partials      811      758      -53     

Files Changed	Coverage Δ
metadata/client.go	84.11% <0.00%> (-0.34%)	⬇️

... and 6 files with indirect coverage changes

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[anthonylasso]

@aolfat I looked and didn't find anything suitable.