MongoDB complex object versioning with Spring Boot

Question

I'm trying to identify the best way to do mongodb object versioning.

Based on the mongodb document versioning pattern, storing revisions in a history collection and having current version in main collection is recommended. According to that, each revision contains the complete object instead of storing diffs.

Then I went through ways to implement data versioning in mongoDB where it recommends a method to store a single document containing all the revisions inside it having a separate history collection.

Therefore, I'm trying to implement my own object versioning implementation for the following document model due its complexity.

Invoice.java

public class Invoice {

    private long invoiceId;

    private String userName;

    private String userId;

    private LocalDateTime createdDate;

    private LocalDateTime lastModifiedDate;

    private List<String> operationalUnits;

    private List<BodyModel> body;

    private List<ReviewModel> reviews;

    private BigDecimal changedPrice;

    private String submitterId;

    private LocalDateTime submittedTime;

    private String approverId;

    private LocalDateTime approvedTime;
}

BodyModel.java

public class BodyModel {

    private String packageId;

    private List<ItemModel> items;

    private List<String> reviews;
}

ReviewModel.java

public class ReviewModel {

    private String publishedTime;

    private String authorName;

    private String authorId;

    private String text;
}

ItemModel.java

public class ItemModel {

    private String itemNumber;

    private String description;

    private String brandId;

    private String packId;

    private List<String> reviews;
}

ER Diagram (Simplified)

At the moment, I'm using Javers library. But, Javers keeps the Invoice model as the main entity and other models such as BodyModel, ReviewModel, ItemModel as separated valueObjects. As a result, instead of creating a single revision document, it creates separated documents for the valueObjects. Additionally, it always constructs the current objects from the base version plus all changes which leads to huge read time. Addtionally, I identified a valueObjects issue that comes with javers. Refer this question for more info: MongoDB document version update issue with JaVers

Following are the issues, I've if I'm going to create my own implementation using spring boot.

1. If I'm going to put revisionId in each of the revisions (as shown in the below object) when mongoDB save(), how do I find the current revisionId to be included ?

{
    _Id: <ObjectId>,
    invoiceId: <InvoiceId>,
    invoice: <Invoice>,
    revisionId: <revisionId>
}

For this I can keep a field for revisionId in InvoiceModel which can be updated when saving to the main collection. And at the same time, it can be used to save the revision into history collection. Is it the best possible way to do it in this case ?

2. If I'm only going to store diffs, then how do I obtain the current version of the object ?

For this, it feels essential to fetch the current object from the main collection and then compare it with new version (I already have the new version, because that's what I'm going to store in main collection) to create the diff. Then diff can be stored in history collection and new version in main collection. Is it the best possible way to store diffs ?

In both scnearios, aspects coming from AOP can be used to intercept the save() method of the base repository to accomplish the task. But I don't mainly consider about coding implementation details, I would like to know which method or methods would be efficient in storing revisions for a data model such as given above (would like to discuss about methods I've mentioned as well) ?