Relying on groovy can be problematic (even now they were quite delayed when it comes to supporting newer Java) and the benefits are not that significant.

What's more:

• better maintenance (compile time checks)
• would help us shave off roughly 20% od dependencies
• would help reduce memory usage.
• would make it easier to use graalvm and native-image

(initially targeted for 9.0.0, depends on eventual http-api adjustments)

For templating we could possibly use jte as it's efficient and small/without further dependencies