Support templates defined in nested classes

[timtebeek]

What problem are you trying to solve?

Nested classes are a convenient way of grouping relevant recipes together, that would otherwise be spread over a large number of files and harder to maintain. Consider the case where we replace StringUtils methods; there it would be convenient to have a wrapper ApacheCommonsStringUtils class that contains multiple nested classes for each of the replaced methods.

When I try to do that now a wrapper Recipe class is generated, but the inner Recipe classes aren't static, so creating instances of those fails with serialization.

Describe the solution you'd like

Static inner classes.

Have you considered any alternatives or workarounds?

Not really; open to suggestions.

Additional context

• Add Apache Commons StringUtils refaster template replacements rewrite-migrate-java#270