refactor conversion category customisation

[grisumbras]

Users are now meant to specialise conversion_category_of.

[cppalliance-bot]

An automated preview of the documentation is available at https://1156.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-04-28 15:32:49 UTC

[cppalliance-bot]

GCOVR code coverage report https://1156.json.prtest2.cppalliance.org/gcovr/index.html
LCOV code coverage report https://1156.json.prtest2.cppalliance.org/genhtml/index.html
Coverage Diff Report https://1156.json.prtest2.cppalliance.org/diff-report/index.html

Build time: 2026-04-28 15:50:22 UTC

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1156/pullrequest.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.66%. Comparing base (a6e9c7b) to head (a7c87b0).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1156   +/-   ##
========================================
  Coverage    93.66%   93.66%           
========================================
  Files           91       91           
  Lines         9325     9325           
========================================
  Hits          8734     8734           
  Misses         591      591           

Files with missing lines	Coverage Δ
include/boost/json/detail/parse_into.hpp	99.33% <ø> (ø)
include/boost/json/detail/value_from.hpp	100.00% <100.00%> (ø)
include/boost/json/detail/value_to.hpp	99.13% <ø> (ø)
include/boost/json/impl/conversion.hpp	100.00% <ø> (ø)
include/boost/json/impl/serializer.hpp	97.79% <ø> (ø)
include/boost/json/impl/serializer.ipp	100.00% <100.00%> (ø)

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[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1156/pullrequest.html

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1156/pullrequest.html