add digest_algorithm option in writer

[ThomasLiennard]

Add new digest_algorithm option to WarcWriter and RecordBuilder to set digest hash algorithm to something other than sha1.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.42%. Comparing base (aa702cb) to head (ec6d33d).
⚠️ Report is 22 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #119   +/-   ##
=======================================
  Coverage   98.42%   98.42%           
=======================================
  Files          18       18           
  Lines        1650     1655    +5     
  Branches      265      266    +1     
=======================================
+ Hits         1624     1629    +5     
  Misses          6        6           
  Partials       20       20           

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[Mr0grog]

This would be lovely to have! Given the notes about encoding in the annotated WARC 1.1 spec, it might be nice if it selected a different encoding (or let you specify an encoding) depending on the algorithm (e.g. base-32 encoding a sha-256 digest might get you a technically invalid header value, so base16 is better for that algorithm).

[wumpus]

Apologies for being so picky after such a long time, but here are some comments:

• pullreqs should be made against the "develop" branch
• the documentation needs to mention this new feature
• this feature needs to work with all ways that warcio creates warcs, including capture_http()
• what do you expect to happen with an invalid digest_algorithm name? You should document and test that so that the new interface will remain stable
• you need to test that warcio check is happy with this digest (very likely, but still test it)
• you have added some end-of-line whitespace; look at "git diff" to see it

[wumpus]

(If you are no longer interested in this PR I'm willing to fix these things)