Sorting documents by multiple attributes is not working correctly

[GurtejSohi]

Problem

When we provide multiple OrderBys in a query, it sometimes returns the documents in an incorrect order. For example, if we try to sort the documents based on field1 and then field2, it works incorrectly in some cases:
query.addAllOrderBys(List.of(new OrderBy("field1", true), new OrderBy("field2", false)));

This is tested using MongoCollection.

Cause

The orderBy list is converted to a HashMap which may not preserve the order of the keys(as in the list) -
https://github.com/hypertrace/document-store/blob/main/document-store/src/main/java/org/hypertrace/core/documentstore/mongo/MongoCollection.java#L365
So, in the above example, it can happen that the sorting happens first on field2 and then on field1.

[GurtejSohi]

One possible solution is that we can use LinkedHashMap instead of HashMap for the orderbyMap.