New Features
- Added the ability to fully preserve the casing of headers (as opposed to normalizing to kebab-style-lowercase) (#5522)
Fixes
- Ensure that enterprise features, when used by an open source user, produce error messages (#4020)
- Remove the Upgradable Plugin interface. This abstraction was a little leaky. Now we handle upgrading plugins in the enterprise application itself, as that is the source of truth for what should be upgraded. (#4367)