build: modularize CMake configuration

[zuudevs]

Summary

Refactors the CMake build system into a modular, target-scoped structure while preserving library behavior and existing CI/package workflows.

Project identity

• raises the CMake minimum to 3.21 so PROJECT_IS_TOP_LEVEL is available
• updates the project version from 0.1.0 to 0.9.0, matching the current development milestone
• keeps C++17 as a target requirement instead of a global compiler setting

Root orchestration

The root CMakeLists.txt now acts only as an orchestrator:

• initialize project options
• initialize target policy
• add production source
• conditionally add tests, benchmarks, examples, install/export rules, and developer tools

Modular CMake layout

Adds/normalizes project modules for:

• options
• project target settings
• warnings
• sanitizers
• IPO/native optimizations
• testing
• benchmarking
• examples
• install/export packaging

All project helper functions use the cpp_request_ prefix.

Target cleanup

• renames the physical production target from generic internal to cpp_request
• keeps cpp_request::cpp_request as the public build/export target
• temporarily keeps cpp_request::internal as a compatibility alias
• warnings, sanitizers, optimization, and clang-tidy are applied directly to project targets and do not leak into the installed target graph

Tests / benchmarks / examples

• tests/CMakeLists.txt becomes a test source inventory using cpp_request_add_test()
• benchmark target setup is centralized in cpp_request_add_benchmark()
• adds cpp_request_add_example() for the upcoming v0.9 examples
• preserves BUILD_TESTING=OFF compatibility by using an explicitly provided BUILD_TESTING value as the default for CPP_REQUEST_BUILD_TESTS

Packaging

• moves all install/export logic into cmake/modules/install.cmake
• moves the package config template to cmake/templates/cpp_requestConfig.cmake.in
• preserves the installed target cpp_request::cpp_request
• preserves the install-tree consumer test

Developer tooling

• namespaced cpp_request_format / cpp_request_format_check targets
• target-scoped clang-tidy integration
• fixes Doxygen configuration and generates its Doxyfile into the build tree
• adds cmake/templates/Doxyfile.in

Source-tree hygiene

Normal CMake configure no longer has any path that generates or rewrites vcpkg.json or other source-controlled files. The old cmake/tools/vcpkg.cmake and unused vcpkg template wiring are removed.

Cleanup

Removes superseded global/legacy modules such as output.cmake, singular warning/sanitizer/optimization modules, and the invalid cmake/templates/CMakeLists.txt wiring.

A cmake/README.md documents the new responsibility boundaries and supported project options.

Scope

This is build-system refactoring only. It does not modify HTTP behavior, public C++ API semantics, response framing, networking, or benchmark definitions.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Skip the package test when install rules are disabled

When CPP_REQUEST_BUILD_TESTS=ON and CPP_REQUEST_ENABLE_INSTALL=OFF—including a subproject that enables tests while retaining the new default of disabled installs—tests/CMakeLists.txt still registers PackageConsumer.InstallAndUse. That test runs cmake --install, then its consumer fails at find_package(cpp_request) because this conditional generated neither the package configuration nor export rules. Guard the package-consumer test with CPP_REQUEST_ENABLE_INSTALL, or prevent this option combination.

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