Make /lists/add support POST with json body

[cdrini]

To support Scott Hewitt's work, and to make consistent with our other APIs, POST /lists/add now supports a JSON body containing the list document. Previously it only supported URL parameters.

Technical

Testing

Tests added.

✅ You can test locally on the local host instance by running this in your browser console while logged in and on localhost:8080

await fetch('/lists/add', {
    method: 'POST',
    headers: {
        'Content-Type': "application/json",
    },
    body: JSON.stringify({
        name: 'foo data',
        description: 'bar',
        seeds: [{'key': '/books/OL1M'}, {'key': '/books/OL2M'}],
    }),
}).then(r => r.json())

Should create the list!

✅ You can also create one using url parameters, like before:

await fetch('/lists/add?name=hello&seeds=OL2M,OL3M', {
    method: 'POST',
    headers: {
        'Content-Type': "application/json",
    },
}).then(r => r.json())

Screenshot

Stakeholders

[codecov-commenter]

Codecov Report

Attention: 54 lines in your changes are missing coverage. Please review.

Comparison is base (a3a6529) 16.62% compared to head (c07c6c1) 16.44%.
Report is 2 commits behind head on master.

Files	Patch %	Lines
...enlibrary/plugins/openlibrary/js/handlers/index.js	0.00%	27 Missing and 7 partials ⚠️
openlibrary/plugins/openlibrary/js/list_books.js	0.00%	16 Missing ⚠️
openlibrary/plugins/openlibrary/js/index.js	0.00%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8455      +/-   ##
==========================================
- Coverage   16.62%   16.44%   -0.18%     
==========================================
  Files          85       86       +1     
  Lines        4416     4476      +60     
  Branches      767      783      +16     
==========================================
+ Hits          734      736       +2     
- Misses       3199     3246      +47     
- Partials      483      494      +11     

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[mekarpeles]

lgtm, reviewed w/ @cdrini