Add initial support for java references for yaml

[nielsdebruin]

What's changed?

This adds initial support for generating references to java type from a Yaml fine in a similar fashion, and with similar limitations, as in:

• Add initial support for java references in application properties file #4697

What's your motivation?

Adding this feature allows existing recipes that support references to be applied to .properties files. For more details see:

• Expand Reference to include .properties and .yml #4681

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

The focus points are almost on to one with the previously referenced implementation of references to Java type in .properties files.

Anyone you would like to review specifically?

@timtebeek @Laurens-W

Any additional context

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

[knutwannheden]

I would have expected this PR to only contain the SourceFileWithReferences implementation in Yaml.Documents and not a generic Reference.Provider implementation. But possibly I have missed something here.

[knutwannheden]

AFAICT this will now try to match any YAML scalar values against the regexp we have for Java identifiers. This seems wrong to me. I don't think there is any need to add this class here. Instead I would expect "domain-specific" implementations like SpringReference which look for type references in specific YAML documents (matching some given file name or similar).

AFAIK Spring also allows config to be in YAML, so maybe we could provide an implementation for that.

[timtebeek]

I'd applied some light polish to the parallel PR in 713ced2 ; would be good to apply those same changes here as well, and resolve the conflicts.

[knutwannheden]

Yes, would be good to update this PR now that the dust has settled a bit regarding the rename refactoring.