Demo project for http_client_requests_active_seconds_count metric issue

Steps to reproduce:

1. Launch wiremock container with pre-configured long-responding endpoint:

docker run -it --rm \
    -p 8080:8080 \
    --name wiremock \
    -v ./wiremock:/home/wiremock \
    wiremock/wiremock:3.9.1

2. Build and launch the app:

./gradlew bootRun

3. Execute cURL request with timeout to simulate request cancellation:

curl --location --request POST 'http://localhost:8876/test' -m 1

4. Query metrics and observe http_client_requests_active_seconds_count having value > 0:

curl --location 'http://localhost:8876/management/prometheus' | grep 'http_client_requests_active_seconds_count'