New buckets for 0.6.0: fix model and migration

src/table/schema.rs

@@ -16,6 +16,9 @@ impl PartitionKey for String {
 	}
 }
 
+/// Values of type FixedBytes32 are assumed to be random,
+/// either a hash or a random UUID. This means we can use
+/// them directly as an index into the hash table.
 impl PartitionKey for FixedBytes32 {
 	fn hash(&self) -> Hash {
 		*self