Document new features and improve documentation (#357)

* Document new feature and update documentation

* Document new feature and update documentation

* Document new feature and update documentation

debezium-server-iceberg-sink/src/main/java/io/debezium/server/iceberg/IcebergChangeEvent.java

@@ -333,8 +333,9 @@ private Schema icebergSchema(boolean createIdentifierFields) {
           // due to inconsistency in the after and before fields.
           // For insert events, only the `before` field is NULL, while for delete events after field is NULL.
           // This inconsistency prevents using either field as a reliable key.
-          throw new DebeziumException("Events are unnested, Identifier fields are not supported for unnested events! " +
-              "Pleas make sure you are using event flattening SMT! or disable identifier field creation!");
+          throw new DebeziumException("Debezium events are unnested, Identifier fields are not supported for unnested events! " +
+              "Pleas enable event flattening SMT see: https://debezium.io/documentation/reference/stable/transformations/event-flattening.html " +
+              " Or disable identifier field creation `debezium.sink.iceberg.create-identifier-fields=false`");
         }
       } else {
         icebergSchemaFields(valueSchema, keySchema, schemaData);

docs/CAVEATS.md

@@ -7,7 +7,8 @@ instead of rewrite data files)
 
 ## No automatic schema evolution
 
-Full schema evaluation is not supported. But sema expansion like field addition is supported,
+Full schema evaluation is not supported, like converting incompatible types. But sema expansion like field addition is
+supported,
 see `debezium.sink.iceberg.allow-field-addition` setting.
 
 ## Specific tables replication