Get locale helpers should return undefined

[MickL]

Clear and concise description of the problem

When using getHeaderLocale(event) or getCookieLocale(event) they will return the configurable fallback (default: 'en-US'). It would be great if they could (optionally) return undefined, too.

Usecase:
I would like to do a flow like this:

1. Try detectLocaleFromAcceptLanguageHeader(event), if none is set:
2. Try getCookieLocale(event), if none is set:
3. Use default fallback locale

Suggested solution

They could accept undefined as a fallback: getHeaderLocale(event, { name: undefined })

Alternative

No response

Additional context

No response

Validations

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