Add snapshot testing, change names of polars handlers

[Carlos-Marques]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
nortech/core/gateways/nortech_api.py	96.07% <100.00%> (ø)
nortech/core/services/signal.py	85.71% <ø> (ø)
nortech/datatools/__init__.py	94.44% <100.00%> (+0.15%)	⬆️
nortech/datatools/handlers/download.py	88.88% <100.00%> (+0.65%)	⬆️
nortech/datatools/handlers/pandas.py	100.00% <100.00%> (ø)
nortech/datatools/handlers/polars.py	94.11% <100.00%> (+0.17%)	⬆️
nortech/datatools/services/nortech_api.py	95.55% <100.00%> (ø)
nortech/derivers/handlers/deriver.py	98.66% <100.00%> (+18.93%)	⬆️
nortech/derivers/services/schema.py	94.44% <100.00%> (+0.15%)	⬆️
nortech/derivers/services/visualize.py	92.85% <100.00%> (+79.81%)	⬆️

... and 1 file with indirect coverage changes