public static String serialize(Map<SchemaChangeType, SchemaChangePolicy> policyMap) {
        Preconditions.checkNotNull(policyMap, "policyMap is null");
        StringJoiner joiner = new StringJoiner(DELIMITER);
        for (Entry<SchemaChangeType, SchemaChangePolicy> kv : policyMap.entrySet()) {
            joiner.add(kv.getKey().getCode() + KEY_VALUE_DELIMITER + kv.getValue().getCode());
        }
        return joiner.toString();
    }
Serialize the policy Map[{@link SchemaChangeType}, {@link SchemaChangePolicy}] to a string

@param policyMap The policy Map[{@link SchemaChangeType}, {@link SchemaChangePolicy}]
@return A string format by 'key1=value1&key2=value2...'
inlong-sort/sort-common/src/main/java/org/apache/inlong/sort/util/SchemaChangeUtils.java