Enhance docs to embed code

Some docs include code snippets from examples. For example the HTTP README.adoc. We should investigate tooling to extract code from examples to avoid duplication and stale docs.

Start by reviewing HTTP README.adoc and the example code snippets it duplicates. Investigate how the examples could provide source content for the documentation, and define what tooling or workflow would prevent the snippets from becoming stale. Done means a concrete approach is documented or implemented and its synchronization behavior is verified.

Written by the indexing model from the issue text.