Reroute requests based token heal/listing (#9939)

When manual healing is triggered, one node in a cluster will 
become the authority to heal. mc regularly sends new requests 
to fetch the status of the ongoing healing process, but a load 
balancer could land the healing request to a node that is not 
doing the healing request.

This PR will redirect a request to the node based on the node 
index found described as part of the client token. A similar
technique is also used to proxy ListObjectsV2 requests
by encoding this information in continuation-token

cmd/admin-handlers.go

@@ -652,6 +652,20 @@ func (a adminAPIHandlers) HealHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if globalIsDistErasure {
+		// Analyze the heal token and route the request accordingly
+		_, nodeIndex, parsed := parseRequestToken(hip.clientToken)
+		if parsed {
+			if proxyRequestByNodeIndex(ctx, w, r, nodeIndex) {
+				return
+			}
+		} else {
+			apiErr := errorCodes.ToAPIErr(ErrHealInvalidClientToken)
+			writeErrorResponseJSON(ctx, w, apiErr, r.URL)
+			return
+		}
+	}
+
 	type healResp struct {
 		respBytes []byte
 		apiErr    APIError