Refactor attribute definition and location

[alexamici]

Closes #88

[codecov-commenter]

Codecov Report

Merging #101 (90ef68e) into main (7080ea4) will decrease coverage by 0.35%.
The diff coverage is 78.57%.

@@            Coverage Diff             @@
##             main     #101      +/-   ##
==========================================
- Coverage   91.46%   91.11%   -0.36%     
==========================================
  Files          12       12              
  Lines         914      923       +9     
  Branches      101      101              
==========================================
+ Hits          836      841       +5     
- Misses         57       61       +4     
  Partials       21       21              

Impacted Files	Coverage Δ
tests/test_30_xarray_backends.py	100.00% <ø> (ø)
xarray_sentinel/esa_safe.py	85.39% <55.55%> (+0.33%)	⬆️
xarray_sentinel/reformat.py	68.00% <60.00%> (-10.95%)	⬇️
tests/test_10_esa_safe.py	100.00% <100.00%> (ø)
xarray_sentinel/sentinel1.py	87.20% <100.00%> (ø)

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