Add Snapshot-read-only isolation support

You can read more about this type of isolation here https://ydb.tech/docs/en/concepts/transactions#modes

repository-ydb-v2/src/main/java/tech/ydb/yoj/repository/ydb/YdbRepositoryTransaction.java

@@ -233,6 +233,10 @@ private TxControl<?> getTxControl() {
             case ONLINE_CONSISTENT_READ_ONLY -> TxControl.onlineRo().setAllowInconsistentReads(false);
             case ONLINE_INCONSISTENT_READ_ONLY -> TxControl.onlineRo().setAllowInconsistentReads(true);
             case STALE_CONSISTENT_READ_ONLY -> TxControl.staleRo();
+            case SNAPSHOT -> {
+                TxControl<?> txControl = (txId != null ? TxControl.id(txId) : TxControl.snapshotRo());
+                yield txControl.setCommitTx(false);
+            }
         };
     }
 

repository/src/main/java/tech/ydb/yoj/repository/db/IsolationLevel.java

@@ -32,7 +32,14 @@ public enum IsolationLevel {
      * An <em>almost</em> recent consistent state of the database. Read only.
      * This level is faster then {@code ONLINE_CONSISTENT_READ_ONLY}, but may return stale data.
      */
-    STALE_CONSISTENT_READ_ONLY("SC");
+    STALE_CONSISTENT_READ_ONLY("SC"),
+
+    /**
+     * All the read operations within a transaction access the database snapshot. Read only.
+     * All the data reads are consistent. The snapshot is taken when the transaction begins,
+     * meaning the transaction sees all changes committed before it began.
+     */
+    SNAPSHOT("SP");
 
     @Getter
     private final String txIdSuffix;