fix(cdc): fail closed on blank DDL validation mode

cdc-service/src/test/java/com/xtrmetl/cdc/replication/SchemaChangeReplicaValidationModeTest.java

@@ -0,0 +1,45 @@
+package com.xtrmetl.cdc.replication;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.jupiter.api.Test;
+import org.springframework.jdbc.core.JdbcTemplate;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+
+class SchemaChangeReplicaValidationModeTest {
+
+    @Test
+    void rejectsBlankValidationModeInsteadOfSilentlyDisablingPolicy() {
+        JdbcTemplate jdbcTemplate = mock(JdbcTemplate.class);
+
+        assertThrows(
+                IllegalArgumentException.class,
+                () -> new SchemaChangeReplicaApplier(
+                        jdbcTemplate,
+                        new ObjectMapper(),
+                        true,
+                        "   ",
+                        "CREATE TABLE,ALTER TABLE,CREATE INDEX",
+                        "DROP TABLE,DROP SCHEMA,DROP DATABASE,TRUNCATE"
+                )
+        );
+    }
+
+    @Test
+    void rejectsNullValidationModeInsteadOfSilentlyDisablingPolicy() {
+        JdbcTemplate jdbcTemplate = mock(JdbcTemplate.class);
+
+        assertThrows(
+                IllegalArgumentException.class,
+                () -> new SchemaChangeReplicaApplier(
+                        jdbcTemplate,
+                        new ObjectMapper(),
+                        true,
+                        null,
+                        "CREATE TABLE,ALTER TABLE,CREATE INDEX",
+                        "DROP TABLE,DROP SCHEMA,DROP DATABASE,TRUNCATE"
+                )
+        );
+    }
+}