New MultiHash class

[mih]

This has factored been factored out from the UrlOperations classes. It simplifies that code and can also be used elsewhere.

Closes #344

[codecov]

Codecov Report

Patch coverage: 95.91% and project coverage change: +0.06 🎉

Comparison is base (9e0d341) 91.92% compared to head (96bea83) 91.98%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #345      +/-   ##
==========================================
+ Coverage   91.92%   91.98%   +0.06%     
==========================================
  Files          84       86       +2     
  Lines        7455     7478      +23     
==========================================
+ Hits         6853     6879      +26     
+ Misses        602      599       -3     

Impacted Files	Coverage Δ
datalad_next/url_operations/ssh.py	53.90% <33.33%> (+0.75%)	⬆️
datalad_next/url_operations/__init__.py	82.35% <100.00%> (-1.40%)	⬇️
datalad_next/url_operations/file.py	91.83% <100.00%> (-0.09%)	⬇️
datalad_next/url_operations/http.py	94.38% <100.00%> (-0.07%)	⬇️
datalad_next/utils/multihash.py	100.00% <100.00%> (ø)
datalad_next/utils/tests/test_multihash.py	100.00% <100.00%> (ø)

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[yarikoptic]

FWIW name MultiHash might be a bit suboptimal since collides with a known https://github.com/multiformats/multihash .

Note that in datalad core we have Digester for AFAIK pretty much the same functionality: https://github.com/datalad/datalad/blob/HEAD/datalad/support/digests.py#L25

[mih]

Yes, I am aware of Digester, but it focuses on file-likes, hence it could not be used for the UrlOperations. This PR only took that original implementation and generalized and moved it into its own piece, because #343 also needs this.

Thanks for pointing out the name clash. I was not aware of this. Right now I think that a utility class conflicting with a package is not optimal indeed, but also not a major problem.