Add HTTP QUERY method support

[quinnj]

Summary

Adds first-class support for the RFC 10008 HTTP QUERY method across HTTP.jl's client and server-facing APIs.

• Adds HTTP.query(...), HTTP.query(client, ...), and HTTP.@client helper support without adding a new bare export.
• Treats QUERY as safe/idempotent for high-level retries and stale reused-connection transport retries.
• Preserves QUERY method and replayable body across 301, 302, 307, and 308 redirects while keeping 303 rewrite behavior to GET.
• Canonicalizes the Accept-Query header and documents QUERY request usage.
• Adds live client/router tests plus redirect, retry, transport, and header coverage.

Validation

• julia --project=. test/runtests.jl
• julia --project=docs docs/make.jl
• Fresh temp-env focused run with clean Reseau 1.3.1 checkout: http_core_tests.jl, http_handlers_tests.jl, http_client_tests.jl, http_client_transport_tests.jl

Note: the local checkout has an untracked manifest pointing at an older dirty ~/.julia/dev/Reseau, so the final focused verification used a temporary clean Reseau 1.3.1 checkout to match the current master compat.

Co-authored by Codex

[codecov]

Codecov Report

❌ Patch coverage is 87.87879% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.82%. Comparing base (a1eb82b) to head (79e4818).

Files with missing lines	Patch %	Lines
src/http_client.jl	60.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1319      +/-   ##
==========================================
+ Coverage   87.67%   87.82%   +0.15%     
==========================================
  Files          30       30              
  Lines       11739    11769      +30     
==========================================
+ Hits        10292    10336      +44     
+ Misses       1447     1433      -14     

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[quinnj]

Reviewed against RFC 10008 — the implementation looks correct and complete.

The redirect matrix is the subtle part and it's exactly right: QUERY is preserved on 301/302/307/308 and only rewritten to GET on 303, matching §2.5 — including the easy-to-miss note that "the exceptions for redirecting a POST as a GET after a 301 or 302 do not apply to QUERY." (Verified the preserved-method path carries the body via _copy_request and is still gated by _redirect_body_replayable, same as 307/308 POST.) Safe + idempotent retry treatment at both the high-level (_retryable_request_method) and stale-connection (_retryable_method) layers, Accept-Query canonicalization, the query/query(client,…)/@client surface with no new bare export, and the e2e router test all check out.

One QUERY-specific nuance worth considering (non-blocking): §2/§2.1 makes Content-Type a hard requirement — a server MUST fail a QUERY whose Content-Type is missing (400), unlike POST where a missing type is usually tolerated. Dict/NamedTuple bodies auto-set application/x-www-form-urlencoded, so those are covered, but a raw string/bytes body relies on the caller to set it (the JSON doc example does). Since a missing type is a guaranteed round-trip-to-400 for QUERY specifically, it might be worth failing fast client-side (a warning, or surfacing it) when a QUERY carries a non-empty body without Content-Type — purely optional.

[findings generated by claude]