Merge branch 'WIP_persy_batch_next' into 'next'

feat: Integration with persy using background ops

See merge request famedly/conduit!231

src/database/abstraction.rs

@@ -15,7 +15,15 @@ pub mod heed;
 #[cfg(feature = "rocksdb")]
 pub mod rocksdb;
 
-#[cfg(any(feature = "sqlite", feature = "rocksdb", feature = "heed"))]
+#[cfg(feature = "persy")]
+pub mod persy;
+
+#[cfg(any(
+    feature = "sqlite",
+    feature = "rocksdb",
+    feature = "heed",
+    feature = "persy"
+))]
 pub mod watchers;
 
 pub trait DatabaseEngine: Send + Sync {