Remove hash value from Datafile GCS metadata

[cortadocodes]

Contents

Breaking changes

• Close Redundant hash value in metadata #148: remove hash_value from Datafile GCS metadata
• When hashing Datafiles, only hash represented file (i.e. stop hashing metadata)
• When hashing Datasets and Manifests, only hash the files contained (i.e. stop hashing metadata)
• Make hash of Hashable instance with _ATTRIBUTES_TO_HASH=None the empty string hash value "AAAAAA=="

Fixes

• Use the empty string hash value for Datafile if GCS crc32c metadata isn't present
• Stop serialising hash value of Manifest, Dataset, and Datafile

Minor improvements

• Remove ability to set custom hash value via kwargs when using Datafile.from_cloud

[codecov-commenter]

Codecov Report

Merging #156 (06b6782) into release/0.1.17 (ee8cc7f) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@                Coverage Diff                 @@
##           release/0.1.17     #156      +/-   ##
==================================================
- Coverage           94.77%   94.76%   -0.01%     
==================================================
  Files                  55       55              
  Lines                1569     1567       -2     
==================================================
- Hits                 1487     1485       -2     
  Misses                 82       82              

Impacted Files	Coverage Δ
octue/mixins/hashable.py	100.00% <100.00%> (ø)
octue/resources/datafile.py	98.06% <100.00%> (-0.03%)	⬇️
octue/resources/dataset.py	100.00% <100.00%> (ø)
octue/resources/manifest.py	94.36% <100.00%> (ø)

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[thclark]

Good; one minor question on a default value of the hash to resolve before merging

[thclark]

This is intentionally default None, rather than EMPTY_STRING_HASH_VALUE?

[cortadocodes]

It was getting set to EMPTY_STRING_HASH_VALUE deeper in Datafile._calculate_hash, but I've now realised I can refactor it so it doesn't have to go deeper at all by changing the default above to EMPTY_STRING_HASH_VALUE 👌