fix serialization of cookies

[karenetheridge]

• only one Cookie header is permitted; all cookies must be in a single string (see https://www.rfc-editor.org/rfc/rfc6265#section-5.4)
• the delimiter between individual cookie-pairs is "; ", not ", " (see https://www.rfc-editor.org/rfc/rfc6265#section-4.2.1)

[kraih]

I think there was a reason we don't do this, but i don't quite remember. Cookie headers had to be split up into multiple headers with the same name and not joined as a string or it caused some bugs. 🤔

Edit: I was mixing up Cookie and Set-Cookie.

[Copilot]

Pull request overview

This PR updates Mojo::Headers cookie handling to comply with RFC 6265 by ensuring cookies serialize as a single Cookie header and use "; " as the cookie-pair delimiter.

Changes:

• Update Mojo::Headers to join multiple Cookie values using "; " (instead of ", "), including special handling in to_string.
• Adjust header value joining logic to treat Cookie differently from other headers.
• Add tests asserting correct Cookie and general header serialization from from_hash.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
t/mojo/headers.t	Adds assertions for to_string output and correct cookie flattening via from_hash/to_hash.
lib/Mojo/Headers.pm	Implements Cookie-specific joining in header() and to_string, and updates append() delimiter behavior.

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[kraih]

The header code is quite performance critical, any CPU cycles you can save will add up.

[karenetheridge]

cleaned up, with unnecessary lc removed:

• in the monkey-patched named subs, $name is always in lowercase
• in append and header, name could be in any case and must be normalized
• in to_string, the names method always returns uppercase names

I also inlined a local variable so a string comparison is done only when needed, and created a local var in the monkey-patched method to avoid a runtime calculation.