introduce DeDuplicationPolicyValidator

src/main/java/com/altinity/clickhouse/sink/connector/deduplicator/DeDuplicationPolicyValidator.java

@@ -0,0 +1,45 @@
+package com.altinity.clickhouse.sink.connector.deduplicator;
+
+import com.altinity.clickhouse.sink.connector.KafkaProvider;
+import org.apache.kafka.common.config.ConfigDef;
+import org.apache.kafka.common.config.ConfigException;
+
+/**
+ * DeDuplicationPolicyValidator validates DeDuplicationPolicy enum values
+ */
+public class DeDuplicationPolicyValidator implements ConfigDef.Validator {
+
+    public DeDuplicationPolicyValidator() {
+    }
+
+    /**
+     * ensureValid is called by framework to ensure the validity
+     * 1. when connector is started or
+     * 2. when validate REST API is called
+     *
+     * @param name
+     * @param value
+     */
+    @Override
+    public void ensureValid(String name, Object value) {
+        assert value instanceof String;
+        final String strValue = (String) value;
+        // The value can be null or empty.
+        try {
+            DeDuplicationPolicy policy = DeDuplicationPolicy.of(strValue);
+        } catch (final IllegalArgumentException e) {
+            throw new ConfigException(DeDuplicationPolicyValidator.class.getName(), value, e.getMessage());
+        }
+    }
+
+    /**
+     * String representation of the validator
+     *
+     * @return
+     */
+    public String toString() {
+        return "What DeDuplication policy is used."
+                + " Allowed values are:"
+                + String.join(",", DeDuplicationPolicy.POLICY_NAMES);
+    }
+}