I'm not entirely convinced on this one -- I get that it's conceptually cleaner, but the end result is longer everywhere? 😬 😩 (and the likelihood of changing the value is slim to none)

(Probably just being overly superficial here -- I'm definitely not going to be a blocker on this. 🙈)

I'm not super strongly attached to this. My train of thought was that this is not a standard header (we defined it as part of our API).

From that perspective, I felt it would be useful to have a const defined that can be used by consumers of our API. We can also use the const to properly document the const; I actually should have added the information from https://github.com/moby/moby/blob/v20.10.8/api/swagger.yaml#L72-L93

Truth is that this started out with me digging into some of the authentication bits, and finding myself repeatedly grep for this string to see where all the auth logic was, and how it differed. The const helped me being lazy and have my IDE do that for me (jump to references) 😇 😂.