Spring Revise generation of aggregated Javadoc in Gradle build

Overview

The Gradle team has brought it to our attention that we should ideally generate aggregated Javadoc along the lines of the example provided by @jjohannes here.

Rationale

Adopting the aforementioned best practice for aggregating Javadoc across projects will...

• make parallel execution and build configuration caching safer/possible
• avoid potential breakage in future versions of Gradle
• introduce greater separation of concerns
• replace the current, hand-crafted approach with something more robust and maintainable

Comment From: sbrannen

@rwinch, does the use of the io.spring.javadoc-aggregate plugin (#24715) make this issue obsolete?

Comment From: rwinch

Yes