Is your feature request related to a problem? Please describe.
I'm trying to minimize diffs when using yaml-diff-patch on OpenAPI specs like

openapi: 3.0.0
paths:
  /models/{model}:
    get:
      # etc

The /models/{model} key gets quoted after a roundtrip.

EDIT: I thought this is an implicit key but I think I misinterpreted the spec, so seems like this is valid?

Question: is it actually a valid key? It seems to parse okay and linting tools seem okay with it. But, I found in your code that you intentionally quote implicit keys containing { or }, and the YAML spec seems pretty clear on this:

In addition, inside flow collections, or when used as implicit keys, plain scalars must not contain the “[”, “]”, “{”, “}” and “,” characters. These characters would cause ambiguity with flow collection structures.

Describe the solution you'd like

If an implicit key like /models/{model} is actually unambiguous, can we have defaultKeyType: 'PLAIN' not quote it?

Describe alternatives you've considered

If using an unquoted key in this form is bad and not technically valid, I'm wondering if there's a good example why it shouldn't be done I can relay back to folks who are outputting YAML in this format?

Additional context