feat(storcon): timeline detach ancestor passthrough (#8353)

Currently storage controller does not support forwarding timeline detach
ancestor requests to pageservers. Add support for forwarding `PUT
.../:tenant_id/timelines/:timeline_id/detach_ancestor`. Implement the
support mostly as is, because the timeline detach ancestor will be made
(mostly) idempotent in future PR.

Cc: #6994

pageserver/client/src/mgmt_api.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 
 use bytes::Bytes;
+use detach_ancestor::AncestorDetached;
 use pageserver_api::{models::*, shard::TenantShardId};
 use reqwest::{IntoUrl, Method, StatusCode};
 use utils::{
@@ -418,6 +419,23 @@ impl Client {
         }
     }
 
+    pub async fn timeline_detach_ancestor(
+        &self,
+        tenant_shard_id: TenantShardId,
+        timeline_id: TimelineId,
+    ) -> Result<AncestorDetached> {
+        let uri = format!(
+            "{}/v1/tenant/{tenant_shard_id}/timeline/{timeline_id}/detach_ancestor",
+            self.mgmt_api_endpoint
+        );
+
+        self.request(Method::PUT, &uri, ())
+            .await?
+            .json()
+            .await
+            .map_err(Error::ReceiveBody)
+    }
+
     pub async fn tenant_reset(&self, tenant_shard_id: TenantShardId) -> Result<()> {
         let uri = format!(
             "{}/v1/tenant/{}/reset",