Proto DataStore - Nested Types

Okay so I've been experimenting with Proto DataStore in Kotlin, and I have one issue. I'm using the following .proto file:

syntax = "proto3";

option java_package = "com.example.protodatastore";
option java_multiple_files = true;

    message Person{
      string name = 1;
      int32 age = 2;
      message Address{
        string street = 3;
        int32 number = 4;
      }
      Address address = 5;
    }

This is my Serializer class:

class MyPreferencesSerializer: Serializer<Person> {
    override fun readFrom(input: InputStream): Person {
        try {
            return Person.parseFrom(input)
        }catch (exception: InvalidProtocolBufferException){
            throw CorruptionException("Cannot read proto.", exception)
        }
    }

    override fun writeTo(t: Person, output: OutputStream) {
        t.writeTo(output)
    }
}

And my Repository:

class MyPreferencesRepository(context: Context) {

    private val dataStore: DataStore<Person> = context.createDataStore(
        "my_pref",
        serializer = MyPreferencesSerializer()
    )

    val readProto: Flow<Person> = dataStore.data
        .catch { exception ->
            // dataStore.data throws an IOException when an error is encountered when reading data
            if (exception is IOException) {
                Log.e("TAG", exception.message.toString())
                emit(Person.getDefaultInstance())
            } else {
                throw exception
            }
        }

    suspend fun updateValue(name: String){
        dataStore.updateData {preferences->
            preferences.toBuilder().setName(name).build()
        }
    }

}

So in my updateValue() method, I can set the name of 'name' field, but I don't have setters for my Address message fields like street and number. Compiler is only showing me getters. On the other side for name and age fields I have setters. How can I use setters for those two Address fields: street, number?

One more question. So basically with Proto DataStore we are serializing/deserializing our custom object with all it's fields, instead of just single primitive types like string, int etc?