axum-extra: Use json!() macro

[Turbo87]

This seems a bit easier to use than the Json(json!(...)) construct and is apparently even a bit faster since it does not need to allocate as much memory.

Related:

• Add axum_extra::json! tokio-rs/axum#2962

[codecov]

Codecov Report

Attention: Patch coverage is 92.94118% with 6 lines in your changes missing coverage. Please review.

Project coverage is 89.16%. Comparing base (fa7b413) to head (deccdc1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/controllers/site_metadata.rs	0.00%	2 Missing ⚠️
src/controllers/team.rs	0.00%	2 Missing ⚠️
src/controllers/krate/metadata.rs	87.50%	1 Missing ⚠️
src/controllers/version/downloads.rs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9960   +/-   ##
=======================================
  Coverage   89.16%   89.16%           
=======================================
  Files         292      292           
  Lines       30316    30316           
=======================================
  Hits        27031    27031           
  Misses       3285     3285           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.