Document Refaster rule & recipe development

[timtebeek]

What problem are you trying to solve?

Allow users to discover Refaster rules as a quick way to get started with recipe development.
Either as a complete solution, or a starting point by copying the generate recipe into src/main.

Describe the solution you'd like

A page describing how Refaster recipe development works, and what that offers as compared to the other ways of defining recipes.

Additional context

Example here: https://github.com/openrewrite/rewrite-migrate-java/blob/v2.0.10/src/main/java/org/openrewrite/java/migrate/apache/commons/lang/ApacheCommonsStringUtils.java#L168-L178

Partially covered here: moderneinc/springboot-migration-workshop#18

Requires the annotation processor here: https://github.com/openrewrite/rewrite-templating

[timtebeek]

@mike-solomon this one might be worthwhile to document & link back to under types of recipes here. Knut knows more if I'm unavailable.