Use cluster recommendations when creating tunnels in the Rust SDK

rs/src/management/cluster_selection.rs

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+/// Describes how the cluster for a tunnel create request was chosen.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum TunnelClusterSource {
+    /// The caller specified the cluster.
+    Explicit,
+    /// The recommendations API returned a cluster.
+    Recommended,
+    /// The recommendations API returned a cluster after rejecting the caller's token.
+    RecommendedAfterAuthRejected,
+    /// The recommendations API remained unauthorized after any anonymous retry.
+    FallbackAuthFailed,
+    /// The recommendations API returned no cluster.
+    FallbackEmpty,
+    /// The recommendations API request failed.
+    FallbackError,
+}
+
+impl TunnelClusterSource {
+    pub(crate) const fn as_header_value(self) -> &'static str {
+        match self {
+            Self::Explicit => "explicit",
+            Self::Recommended => "recommended",
+            Self::RecommendedAfterAuthRejected => "recommended-after-auth-rejected",
+            Self::FallbackAuthFailed => "fallback-auth-failed",
+            Self::FallbackEmpty => "fallback-empty",
+            Self::FallbackError => "fallback-error",
+        }
+    }
+
+    /// Gets whether global routing was used instead of a recommendation.
+    pub const fn is_fallback(self) -> bool {
+        matches!(
+            self,
+            Self::FallbackAuthFailed | Self::FallbackEmpty | Self::FallbackError
+        )
+    }
+}