[BUG] Fragments/anchors are removed from URL

[bourquep]

Describe the bug

I am implementing a Refit client for the Mixpanel API. Many of their API endpoints contain a fragment (aka anchor, hashtag, pound), like this:

My Refit declaration for the above API is:

[Post("/engage#profile-set")]
Task<ApiResponse<int>> SetPropertiesAsync(
  [Body(BodySerializationMethod.UrlEncoded)] UserProfileSetRequest request,
  CancellationToken ct);

However, when I run this and inspect the underlying HttpRequestMessage, the #profile-set part of the URL is missing, and the API call fails.

Expected behavior

URL fragments should be preserved.

Environment

• OS: macOS Monterey 12.0.1
• Device: 2019 Intel MacBook Pro
• Version: 6.1.15