mapstruct-protobuf3 use lombok:UnsupportedOperationException(Collections$UnmodifiableCollection)

还没有人认领这个 Issue。

modify mapstruct-protobuf3/usage/pom.xml plugin config,

org.mapstruct
mapstruct-processor
${org.mapstruct.version}

org.projectlombok
lombok
${org.projectlombok.version}

org.projectlombok
lombok-mapstruct-binding
${lombok-mapstruct-binding.version}

org.mapstruct.examples.spi
protobuf-spi-impl
1.0.0

`

rebuild the mapstruct-protobuf3, run the test,report an error
`java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableCollection.addAll(Collections.java:1065)
at org.mapstruct.example.mapper.UserMapperImpl.map(UserMapperImpl.java:34)
at org.mapstruct.example.ProtobufTest.test(ProtobufTest.java:33)，`

Partially generated code

```
if ( userDTO.getMainDepartmentsList() != null ) {
List list = departmentListToDepartmentDTOList( user.getMainDepartments() );
if ( list != null ) {
userDTO.getMainDepartmentsList().addAll( list );
}

}
if ( userDTO.getDepartmentsList() != null ) {

List list1 = departmentListToDepartmentDTOList( user.getDepartments() );
if ( list1 != null ) {
userDTO.getDepartmentsList().addAll( list1 );
}
```

recover mapstruct-protobuf3/usage/pom.xml plugin config, run test success.
Is there any way to solve this problem?

从 mapstruct-protobuf3/usage/pom.xml 开始，检查 issue 中所示的 annotationProcessorPaths 配置。重新构建 mapstruct-protobuf3 示例并运行 mapstruct-protobuf3/usage/src/test/.../ProtobufTest.java，检查生成的 UserMapperImpl.java 代码，并确认测试在没有 UnsupportedOperationException 的情况下完成。

由索引模型根据 Issue 内容生成。