Add breaking change to 4.0 migration guide: Option arity feature has been removed

[ThomasVitale]

In 4.0, option arity is not a supported feature anymore. After going through the docs and the source code, I could infer the way to replace it was to use arguments instead of options. I like the new feature for being able to pass extra arguments without having to define a named option as it offers a better user experience. However, it would be great if this breaking change was highlighted in the 4.0 migration guide, together with some hints about how to replace it when migrating to Spring Shell 4.0. For me, it wasn't immediately clear. I had to go through docs and code to figure out the right way to migrate my code. And I probably did it wrong. I found a @Arguments annotation which is not mentioned in the docs and I'm probably using it wrong because it doesn't seem to make the arguments actually parsed into a List<String>.

[georgmittendorfer]

I did run into the same issue. Replacing with arguments would not work for me. I can live without arity but a mention in the migration guide would have saved some time.