[2nd viz] GraphQL query for createdBoxes

[pylipp]

This brings the new public GraphQL query createdBoxes.

The interface has been defined in #898.

Please verify that you can run a query like

query { createdBoxes { facts { boxesCount } dimensions { product { id } category { id } } } }

without errors. In the response facts is expected to contain several elements; dimensions returns sensible data, too.

Note that the implementation is not precise with regards to possible changes in box product or item count that might have happened since creation.

[codecov]

Codecov Report

Merging #917 (2dcdc04) into master (f9b35ec) will increase coverage by 0.05%.
The diff coverage is 95.00%.

❗ Current head 2dcdc04 differs from pull request most recent head 5654021. Consider uploading reports for the commit 5654021 to get more accurate results

@@            Coverage Diff             @@
##           master     #917      +/-   ##
==========================================
+ Coverage   71.25%   71.30%   +0.05%     
==========================================
  Files         285      285              
  Lines        7214     7232      +18     
  Branches     1521     1525       +4     
==========================================
+ Hits         5140     5157      +17     
  Misses       2040     2040              
- Partials       34       35       +1     

Flag	Coverage Δ
backend	96.90% <95.00%> (-0.02%)	⬇️
frontend	51.70% <ø> (ø)

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Files Changed	Coverage Δ
back/boxtribute_server/exceptions.py	92.18% <ø> (ø)
...oxtribute_server/business_logic/statistics/crud.py	96.96% <93.33%> (-3.04%)	⬇️
...ribute_server/business_logic/statistics/queries.py	100.00% <100.00%> (ø)
back/boxtribute_server/graph_ql/schema.py	100.00% <100.00%> (ø)