Add support for Mongo's Decimal128 data type

New Feature / Enhancement Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.

Current Limitation

Current Parse Server "Number" data type only supports numbers up to Mongo's double data type max value

Feature / Enhancement Description

Mongo 3.4 added support for Decimal128, adding support for it would allow servers to store numbers that they couldn't store before, all while keeping all query functions still working (afaik Decimal128 supports $gt, $gte, $lt, $lte, $eq, etc...)

Implementation I think would be very straightforward, the problem with this data type that it's not natively supported in all SDKs, so Parse Server would probably need to send the Decimal128 as a string in the Response and the SDK would need to convert the string back to a BigDecimal class (probably available in all languages)

Another problem is to find another alternative for Postgres, but I am no expert in Postgres so idk..

Example Use Case

I think any app that deals with monetary values need this data type, most blockchains use uint256 (max value of 2^256-1) for value representation...

Alternatives / Workarounds

You can store big numbers using strings right now, but that doesn't support number specific query functions...

References

https://www.mongodb.com/developer/products/mongodb/bson-data-types-decimal128/
https://github.com/iriscouch/bigdecimal.js/tree/master
https://pub.dev/packages/decimal

Start by tracing how Parse Server currently represents Number values and handles numeric queries, then compare MongoDB Decimal128 behavior with the PostgreSQL path and SDK serialization constraints described in the issue. Done means large decimal values can be stored, queried, and returned consistently across supported backends and clients.