feat: partial imports, off values as control value

[khvn26]

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Changes

Closes #2838.

• Remove transaction from the import task
• Create control values for mulrivariate features from LD's off values
• Generic error logging

How did you test this code?

Modified relevant unit tests.

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[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (b0ef013) 95.60% compared to head (6ad60ff) 95.61%.
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2864   +/-   ##
=======================================
  Coverage   95.60%   95.61%           
=======================================
  Files        1009     1009           
  Lines       28904    28910    +6     
=======================================
+ Hits        27634    27641    +7     
+ Misses       1270     1269    -1     

Files	Coverage Δ
api/integrations/launch_darkly/services.py	100.00% <100.00%> (ø)
...s/unit/integrations/launch_darkly/test_services.py	100.00% <100.00%> (ø)
api/integrations/launch_darkly/tasks.py	71.42% <0.00%> (+4.76%)	⬆️

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