refactor: remove dotenv-cpp dependency from integration tests

Replace dotenv::getenv() calls with a local getenv_or() lambda wrapping
std::getenv(), using the same key/fallback pattern. This removes the
laserpants/dotenv-cpp FetchContent fetch, the dotenv link target, and
the <dotenv.h> include entirely.

The integration test already receives all connection parameters via
process environment variables set by CMake set_tests_properties(), so
no .env file loading was actually needed at runtime.

Also remove dotenv-cpp from README.md dependencies list.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Pierre-Luc Gagné

README.md

@@ -215,7 +215,6 @@ Automatically fetched via CMake FetchContent:
 
 - [Boost.PFR](https://github.com/boostorg/pfr) — compile-time struct reflection (header-only)
 - [boost.ut](https://github.com/boost-ext/ut) v2.1.0 — unit testing (test builds only)
-- [dotenv-cpp](https://github.com/laserpants/dotenv-cpp) — `.env` file loading (integration tests only)
 
 System dependencies:
 

tests/integration/CMakeLists.txt

@@ -14,19 +14,6 @@ if(NOT TARGET Boost::ut)
     FetchContent_MakeAvailable(boost_ut)
 endif()
 
-# dotenv-cpp (header-only, for .env file loading in integration tests)
-if(NOT TARGET dotenv)
-    include(FetchContent)
-    set(BUILD_DOCS OFF CACHE BOOL "Disable dependency docs generation" FORCE)
-    FetchContent_Declare(
-        laserpants_dotenv
-        GIT_REPOSITORY https://github.com/laserpants/dotenv-cpp.git
-        GIT_TAG master
-        GIT_SHALLOW TRUE
-    )
-    FetchContent_MakeAvailable(laserpants_dotenv)
-endif()
-
 find_package(PkgConfig REQUIRED)
 
 # Add integration test cmake modules path
@@ -45,7 +32,6 @@ target_link_libraries(tests_integration_ds_mysql
     PRIVATE
         ds_mysql
         Boost::ut
-        dotenv
 )
 
 # Link with MySQL client library

tests/integration/mysql/test_query_builder.cpp

@@ -1,7 +1,6 @@
-#include <dotenv.h>
-
 #include <boost/ut.hpp>
 #include <chrono>
+#include <cstdlib>
 #include <optional>
 #include <string>
 #include <vector>
@@ -43,18 +42,23 @@ struct trade {
 };
 
 [[nodiscard]] std::optional<mysql_config> mysql_config_from_env() {
-    const std::string host = dotenv::getenv("DS_MYSQL_TEST_HOST", "");
-    const std::string database = dotenv::getenv("DS_MYSQL_TEST_DATABASE", "ds_mysql_test");
-    const std::string user = dotenv::getenv("DS_MYSQL_TEST_USER", "");
-    const std::string password = dotenv::getenv("DS_MYSQL_TEST_PASSWORD", "");
+    auto getenv_or = [](char const* key, char const* fallback = "") -> std::string {
+        char const* v = std::getenv(key);
+        return v ? v : fallback;
+    };
+
+    const std::string host     = getenv_or("DS_MYSQL_TEST_HOST");
+    const std::string database = getenv_or("DS_MYSQL_TEST_DATABASE", "ds_mysql_test");
+    const std::string user     = getenv_or("DS_MYSQL_TEST_USER");
+    const std::string password = getenv_or("DS_MYSQL_TEST_PASSWORD");
 
     if (host.empty() || user.empty() || password.empty()) {
         return std::nullopt;
     }
 
-    const std::string port_env =
-        dotenv::getenv("DS_MYSQL_TEST_PORT", std::to_string(default_mysql_port.to_unsigned_int()));
-    const auto parsed_port = static_cast<unsigned int>(std::stoul(port_env));
+    const std::string port_str =
+        getenv_or("DS_MYSQL_TEST_PORT", std::to_string(default_mysql_port.to_unsigned_int()).c_str());
+    const auto parsed_port = static_cast<unsigned int>(std::stoul(port_str));
 
     return mysql_config{
         host_name{host},