Introduce customs updates

meilidb-core/src/update/customs_update.rs

@@ -0,0 +1,26 @@
+use crate::{store, error::UnsupportedOperation, MResult};
+use crate::update::{Update, next_update_id};
+
+pub fn apply_customs_update(
+    writer: &mut rkv::Writer,
+    main_store: store::Main,
+    customs: &[u8],
+) -> MResult<()>
+{
+    main_store.put_customs(writer, customs)
+}
+
+pub fn push_customs_update(
+    writer: &mut rkv::Writer,
+    updates_store: store::Updates,
+    updates_results_store: store::UpdatesResults,
+    customs: Vec<u8>,
+) -> MResult<u64>
+{
+    let last_update_id = next_update_id(writer, updates_store, updates_results_store)?;
+
+    let update = Update::Customs(customs);
+    updates_store.put_update(writer, last_update_id, &update)?;
+
+    Ok(last_update_id)
+}