Introduce the concept of a best-practice representation?

[halostatue]

Right now, MIME::Types has two main representations of a MIME content type:

• content_type: a presentation value from the MIME type registry and should not be used for comparison. The case of the content type is preserved, and extension markers (x-) are kept.
• simplified: a comparison value, mostly used for sorting. It strips extension markers (x-) and converts to lowercase. The problem here is that application/x-www-url-form-encoded must have the x- present or it is incorrect, even though this fixes for the case of audio/QCELP sorting too early because of the capitalization of QCELP.

Should there be a best-practice representation created as well (see #76, #80)? This might be:

• best_practice (or mime_type): a lowercase representation of content_type. This would protect the sort of audio/QCELP and keep application/x-www-url-form-encoded legit.

[halostatue]

Keeping this open for now. I do not think that I will introduce a new representation but a new flag could be introduced, exact, which indicates that the content_type can only be simplified as itself. Alternatively, we could indicate that a registered type has no simplified representation (negating the need for a new flag).

This would specifically prevent the mangling of several types (these are from application/ as an example):

name	template	reference
x-pki-message	application/x-pki-message	[RFC8894]
x-www-form-urlencoded	application/x-www-form-urlencoded	[WHATWG][Anne_van_Kesteren]
x-x509-ca-cert	application/x-x509-ca-cert	[RFC8894]
x-x509-ca-ra-cert	application/x-x509-ca-ra-cert	[RFC8894]
x-x509-next-ca-cert	application/x-x509-next-ca-cert	[RFC8894]

This would be a fairly major change, so it maywill not happen until v4.