feat: If DeclarativeRecipe only has already-initialized recipes, don't require initialization

[kmccarp]

What's changed?

I've updated the way that DeclarativeRecipe.validate() works. Before, it was always required to call DeclarativeRecipe.initialize() in order to validate that all recipes were initialized before using the recipe.

What's your motivation?

There are use cases where a DeclarativeRecipe can be constructed with already-instantiated recipe objects. In this case, we don't want to require initialization.

Anything in particular you'd like reviewers to focus on?

N/A

Anyone you would like to review specifically?

@sambsnyd

Have you considered any alternatives or workarounds?

Yes, the most important part here was to fix a null pointer. Before this change, the validation code was as follows:

        return Validated.<Object>test("initialization",
                        "initialize(..) must be called on DeclarativeRecipe prior to use.",
                        this, r -> initValidation != null)
                .and(validation)
                .and(initValidation);

If initialize was not called, then initValidation would be null. the .and(initValidation) would throw a NullPointerException.

The most important aspect of this PR was to fix that NullPointerException, and I considered doing so and keeping the validation the same otherwise:

        return Validated.<Object>test("initialization",
                        "initialize(..) must be called on DeclarativeRecipe prior to use.",
                        this, r -> initValidation != null)
                .and(validation)
                .and(initValidation == null ? Validated.none() : initValidation);

This would have the effect that a DeclarativeRecipe that didn't have .initialize() called on it would still throw a warning, but not blow up.

Any additional context

N/A

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files