Fix bug where enum for s3 select was using NotBlank annotation

Signed-off-by: Taylor Gray <tylgry@amazon.com>

Author: graytaylor0

data-prepper-plugins/s3-source/src/main/java/org/opensearch/dataprepper/plugins/source/configuration/S3SelectOptions.java

@@ -5,8 +5,8 @@
 package org.opensearch.dataprepper.plugins.source.configuration;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
-
 import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
 
 /**
  * Class consists the s3 select options.
@@ -24,7 +24,7 @@ public class S3SelectOptions {
 	private String expressionType = DEFAULT_EXPRESSION_TYPE;
 
 	@JsonProperty("input_serialization")
-	@NotBlank(message = "input serialization format cannot be null or empty")
+	@NotNull
 	private S3SelectSerializationFormatOption s3SelectSerializationFormatOption;
 
 	@JsonProperty("compression_type")