doc: examples use declarative configuration 3/N

[coryan]

Part of the work for #345

[codecov]

Codecov Report

Merging #369 (c1fdc6d) into main (9761987) will increase coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head c1fdc6d differs from pull request most recent head c1caa33. Consider uploading reports for the commit c1caa33 to get more accurate results

@@            Coverage Diff             @@
##             main     #369      +/-   ##
==========================================
+ Coverage   88.91%   88.96%   +0.04%     
==========================================
  Files          97       97              
  Lines        3031     3044      +13     
==========================================
+ Hits         2695     2708      +13     
  Misses        336      336              

Impacted Files	Coverage Δ
...concepts_after_response/concepts_after_response.cc	100.00% <100.00%> (ø)
...e/concepts_after_timeout/concepts_after_timeout.cc	100.00% <100.00%> (ø)
...es/site/concepts_filesystem/concepts_filesystem.cc	100.00% <100.00%> (ø)
examples/site/concepts_request/concepts_request.cc	100.00% <100.00%> (ø)
...ples/site/concepts_stateless/concepts_stateless.cc	100.00% <100.00%> (ø)
examples/site_test.cc	98.52% <100.00%> (+0.03%)	⬆️

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