+=head1 KNOWN PROBLEMS
+
+ * It's not currently possible to identify allocations between requests, for
+ example for presenting the user possible allocations and then actually using
+ them on the next request.
+ * It's not currently possible to give C<allocate> prior constraints.
+ Currently all constraints are treated as hints (and will be preferred) but
+ the internal ordering of the hints is fixed and more complex preferentials
+ are not supported.
+ * bestbefore handling is untested
+