feat(http): auto User-Agent + custom-headers override

[johnpmitsch]

Summary

• Every outbound HTTP request now carries an auto-generated User-Agent of the form quicknode-sdk-<lang>/<sdk-version> (<os>-<arch>; <lang>-<runtime-version>). Each binding (Python, Node, Ruby) supplies its own ClientInfo so the user agent identifies the package the caller actually installed — npm 3.x.y, PyPI a27, gem alpha.27, etc. — not the underlying Rust core.
• HttpConfig gains an optional headers map. Caller-supplied headers override every SDK-managed header (User-Agent, x-api-key, Accept, Content-Type); docblocks call this out explicitly. Maximum flexibility — trust the caller.
• Ruby additionally gets QuicknodeSdk::SDK.from_config(opts) so it matches the Python/Node explicit-config surface and can set headers without env vars.

these are the exact strings for default user-agent header the SDK will use on Apple Silicon macOS (darwin/aarch64), built against the current 0.1.0-alpha.27 train. The is the language-package version,
not the Rust core version.

  - Rust
  quicknode-sdk-rust/0.1.0-alpha.27 (macos-aarch64; rust-1.85)
  (rustc version comes from CARGO_PKG_RUST_VERSION — the MSRV. Falls back to unknown if unset.)
  - Python (CPython 3.12.4 on macOS arm64)
  quicknode-sdk-python/0.1.0a27 (macos-aarch64; python-3.12.4)
  (Python version reads sys.version_info; SDK version reads importlib.metadata.version("quicknode-sdk") — PyPI uses PEP 440, so 0.1.0-alpha.27 → 0.1.0a27.)
  - Node (Node 20.10.0 on macOS arm64)
  quicknode-sdk-node/3.1.0-alpha.27 (macos-aarch64; node-20.10.0)
  (Node version reads process.version, stripping the leading v. SDK version is 3.x.y because @quicknode/sdk 2.x already shipped on npm — release-bump translates 0.x.y → 3.x.y.)
  - Ruby (Ruby 3.3.0 on macOS arm64)
  quicknode-sdk-ruby/0.1.0-alpha.27 (macos-aarch64; ruby-3.3.0)
  (Ruby version reads RUBY_VERSION; SDK version comes from s.version in the gemspec.)

On Linux x86_64 the platform segment changes to linux-x86_64; on aarch64 Linux it's linux-aarch64. Those values come from std::env::consts::{OS, ARCH} in the core crate, so the binding language
doesn't affect them.

Custom header override examples

Rust

use std::collections::HashMap;
use quicknode_sdk::{HttpConfig, QuicknodeSdk, SdkFullConfig};

let mut headers = HashMap::new();
headers.insert("X-Correlation-Id".to_string(), "abc-123".to_string());
headers.insert("User-Agent".to_string(), "my-app/1.0".to_string()); // overrides SDK default

let qn = QuicknodeSdk::new(
    &SdkFullConfig::builder()
        .api_key("your-key")
        .http(HttpConfig { headers: Some(headers), ..Default::default() })
        .build(),
)?;

Python

from sdk import QuicknodeSdk, SdkFullConfig, HttpConfig

qn = QuicknodeSdk(
    SdkFullConfig(
        api_key="your-key",
        http=HttpConfig(headers={
            "X-Correlation-Id": "abc-123",
            "User-Agent": "my-app/1.0",  # overrides SDK default
        }),
    )
)

Node

import { QuicknodeSdk } from "@quicknode/sdk";

const qn = new QuicknodeSdk({
  apiKey: "your-key",
  http: {
    headers: {
      "X-Correlation-Id": "abc-123",
      "User-Agent": "my-app/1.0", // overrides SDK default
    },
  },
});

Ruby

qn = QuicknodeSdk::SDK.from_config(
  api_key: "your-key",
  http: {
    headers: {
      "X-Correlation-Id" => "abc-123",
      "User-Agent" => "my-app/1.0", # overrides SDK default
    },
  },
)

Fixes DX-5042
Fixes DX-5302

Test plan

• cargo check && just lint && just test (203 unit tests pass; new tests cover default UA shape, language-binding UA shape, custom-header overrides, invalid header name/value, and a wiremock test asserting both UA and custom headers reach the wire)
• just python-build (stubs regenerated with the new headers parameter)
• just node-build (index.d.ts regenerated with the new headers field; existing test suite passes)
• just ruby-build (smoke-tested QuicknodeSdk::SDK.from_config(api_key:, http: { headers: ... }) constructs cleanly)
• Run each language's e2e example end-to-end against the live API with QN_API_KEY set:
  • cargo run --example admin_e2e -p quicknode-sdk --features rust
  • uv run python/examples/admin.py
  • cd npm && npx tsx examples/admin.ts
  • ruby ruby/examples/admin_e2e.rb
• Verify the server-side telemetry shows the new User-Agent shape after a release.