alpaca-cpp v0.2.0

Adds the option data streams as a second library, alpaca-options-streaming-cpp, and moves
the SDK onto slick-net 4.

Added

alpaca-options-streaming-cpp

• option_data_stream — real-time option trades and quotes on the indicative and opra
  feeds. Alpaca serves these in MessagePack only, which is why they live in their own
  library: msgpack-cxx is a private, header-only dependency of it and never reaches the base
  SDK or anything that links the library.
• Same interface and behaviour as the JSON streams: on_trade / on_quote handlers,
  subscribe_* / unsubscribe_*, reconnect with re-authentication and subscription replay,
  and the same on_error / on_subscription control handling. Trades and quotes arrive as
  the alpaca::trade and alpaca::quote the REST option methods return.
• Frames are decoded with a SAX parser straight into the handler arguments, with no
  intermediate document. The decoder's parse state and the trade, quote and symbol string
  handed to handlers are reused from message to message, so the message path stops
  allocating once warm — handlers must copy whatever has to outlive the callback.
• Timestamps accept all three MessagePack timestamp encodings as well as RFC-3339 text;
  unknown keys and nested values are skipped, so fields Alpaca adds later are harmless.
• No Content-Type: application/msgpack header is sent on the websocket upgrade, although
  Alpaca's documentation asks for one: slick-net cannot add headers to that request, and the
  option endpoints answer in MessagePack when no Content-Type is given. A JSON text frame is
  routed to the JSON path, so if that default ever changed, Alpaca's refusal would surface
  through on_error instead of as an undecodable frame.
• stream_option_data example.
• 38 offline tests — packed frames, a byte-for-byte hand-encoded frame, and control and data
  frames captured from Alpaca's servers — plus 5 integration tests against the indicative
  feed covering the handshake, rejected credentials, the subscription echo, unsubscribe and
  the 413 refusal of wildcard quote subscriptions. None of them need the market to be open.

Core

• data_client::env() and data_client_awaitable::env(), matching trading_client::env().
  The environment was already stored but unreadable, which is also what made Clang warn
  about an unused private field.
• detail::stream_base extension points for streams that do not speak JSON: virtual
  handle_frame, encode and auth_frame, and an outbound frame_type (text or binary)
  taken by the constructor and reported by outbound_frame_type(). The JSON streams keep
  the defaults and behave exactly as before.

Changed

• slick-net 4.1.1 is required (was 3.1.0), both by the build and by the installed
  alpaca-cppConfig.cmake. Three of its changes reach applications through this SDK:
  • TLS certificates are verified on every https:// and wss:// connection. slick-net
    3.x did not verify them; a TLS-intercepting proxy or a private CA now has to be trusted
    explicitly.
  • slick-net no longer installs process-wide SIGINT / SIGTERM handlers. An application
    that relied on Ctrl-C shutting down its streams has to handle the signal itself, as the
    examples do.
  • Release archives are no longer compiled with -march=native unless slick-net is built
    with SLICK_NET_ENABLE_NATIVE_ARCH=ON, so a prebuilt archive runs on any CPU again.
• With slick-net 4.1.1 the vcpkg ports tree has to be reasonably current. One older than
  slick-stream-buffer-multiplexer 2.2.0 fails configure with
  cannot create ALIAS target "slick::slick-queue" because target "slick::queue" is itself an ALIAS: slick-net fetches the multiplexer and the slick-queue 2.3.0 it needs, then its own
  unversioned find_package(slick-queue) loads vcpkg's older slick-queue too. Updating vcpkg
  fixes it; the README gives a flag-only workaround.
• The test suite requires slick-logger 2.3.0 (was 1.1.0).
• BUILD_ALPACA_OPTIONS_STREAMING defaults to ON, so a default build now needs msgpack-cxx
  (vcpkg msgpack, with a FetchContent fallback). Set it to OFF to build without it.
• CI builds and tests the options-streaming library on every job, and its install-and-consume
  job links the installed alpaca-options-streaming-cpp without looking for msgpack. Release
  archives include the library.
• CI and the release workflow install their dependencies through one composite action,
  .github/actions/install-vcpkg-dependencies. It moves the runner's preinstalled vcpkg to a
  pinned ports commit and bootstraps the matching tool before installing, because the
  images' own vcpkg was old enough to hit the slick-queue configure failure above. The action
  holds the package list and the binary-cache key too, so every job resolves the same
  versions and bumping the pin starts a fresh cache.

Fixed

• Linux Clang builds no longer fail to link slick::net::Websocket's constructor. vcpkg
  builds libslick-net.a with the system GCC, and GCC and Clang mangle the constructor's
  trailing requires std::default_initializable<BufferT> into different symbol names, so a
  Clang consumer of that archive is left with an undefined reference. The CI Clang job now
  builds slick-net from source with the same compiler
  (-DCMAKE_DISABLE_FIND_PACKAGE_slick-net=ON); the same flag is the fix for anyone
  building with Clang against a GCC-built slick-net, and it is documented in the README.
• The Linux Release jobs no longer abort with SIGILL in every test that constructs a
  stream. slick-net 3.1.0's CMakeLists.txt set CMAKE_CXX_FLAGS_RELEASE to
  -O3 -march=native, so vcpkg's libslick-net.a carried whatever instruction set the runner
  that built it happened to have; vcpkg's ABI hash does not cover the host CPU, so the
  workflow's archive cache replayed that build on runners with a narrower one and the
  Websocket constructor — the first frame outside this SDK's own objects — executed an
  unsupported instruction. Those jobs build slick-net from source with
  -DCMAKE_DISABLE_FIND_PACKAGE_slick-net=ON, and slick-net 4.x, now the minimum, no longer
  enables -march=native by default.