Add proxy configuration support to Frends.HTTP.Request

[Copilot]

This adds proxy support to Frends.HTTP.Request by exposing proxy URL and credentials in task options and wiring them into the underlying HTTP handler. It also updates client caching so proxy-specific clients are not reused across incompatible configurations.

• Proxy options

  • Added ProxyUrl, ProxyUsername, and ProxyPassword to request options.
  • Keeps proxy configuration explicit at the task level instead of relying on ambient machine settings.

• HTTP handler configuration

  • Configures HttpClientHandler.Proxy and enables proxy usage when ProxyUrl is provided.
  • Applies proxy credentials when ProxyUsername is set.

• HttpClient cache isolation

  • Extends the HTTP client cache key with proxy settings so cached clients are separated by proxy configuration.
  • Hashes the proxy password in the cache key rather than embedding the raw secret.

• Versioning and release notes

  • Bumps the package version from 1.10.0 to 1.11.0.
  • Adds a changelog entry describing proxy support.

• Coverage

  • Adds unit coverage for proxy handler setup.
  • Adds unit coverage ensuring proxy settings affect the cache key without exposing the raw password.

var options = new Options
{
    ProxyUrl = "http://proxy.example.com:8080",
    ProxyUsername = "proxy-user",
    ProxyPassword = "proxy-password"
};