The Mongoid documentation has a section called "upgrading Mongoid": https://docs.mongodb.com/mongoid/master/tutorials/mongoid-upgrade/

This is very sparsely populated to the point of not being terribly useful. During the 7.0 release cycle (last 2 years) we have only been populating release notes on github (https://github.com/mongodb/mongoid/releases) but the github release notes have a couple of issues:

1. They are arranged in chronological order which means patch versions from different feature versions are mixed (7.1/7.0/6.4).
2. The "new features" section is largely duplicated between a RC release and the upcoming GA release. Yet, there may be important changes for developers in each RC release.
3. They are separate from our main documentation which makes them less discoverable (https://jira.mongodb.org/browse/DOCS-11633).

I like the Java driver release notes (https://mongodb.github.io/mongo-java-driver/4.0/whats-new/) but in practical terms it will be a lot of effort for us to produce that level of detail immediately, especially retroactively for releases already made. (Note the Java driver does not create these 'whats-new' release notes for patch releases).

As the first step I propose going through release notes in the 7.0 branch of Mongoid and incorporating them into https://docs.mongodb.com/mongoid/master/tutorials/mongoid-upgrade/. Release notes for RC versions will be consolidated into release notes for the corresponding GA versions, since users generally won't care about RC releases once GA is released. The focus of this work will be on new features and significant user-visible changes.

If this effort is successful we can expand the level of detail for the 7.1 releases.

A related issue is what to call the page at https://docs.mongodb.com/mongoid/master/tutorials/mongoid-upgrade/. It is more of a list of changes than an upgrade guide; hence it may be appropriate to rename it to something like "Changes in Versions", "Changelog" or simply "Changes".

Some of the related discussion has occurred in https://github.com/mongodb/mongoid/pull/4732.