chore: Add null client (#111)

Adding a null client to allow for table doc generation

Author: mnorbury

lib/src/main/java/io/cloudquery/schema/NullClient.java

@@ -0,0 +1,15 @@
+package io.cloudquery.schema;
+
+import io.cloudquery.messages.WriteMessage;
+
+public class NullClient implements ClientMeta {
+  @Override
+  public String getId() {
+    return "null-client";
+  }
+
+  @Override
+  public void write(WriteMessage message) {
+    // No-op for null client
+  }
+}