Allow for two headers to be set when pulling a formula

[ctompkinson]

A detailed description of the proposed feature

Currently, you cannot set more than one header when using homebrew, see:
https://github.com/Homebrew/brew/blob/master/Library/Homebrew/download_strategy.rb#L424

I would like to be able to set two or more headers on a homebrew request

The motivation for the feature

Currently, I am using homebrew as a private repository and would like to pull some built artefacts from Github but that requires the header Accept: application/octet-stream but as per deprecation notices from github for the URL parameter access_token I should also use the header Authorization: token TOKEN

Currently, this isn't possible as you can only set one header :(

How the feature would be relevant to at least 90% of Homebrew users

It makes it difficult to comply with github deprecation notices and have a private repository

What alternatives to the feature have been considered

I'd have to move from github to separate system for storing my artefacts (not releases) which would be a hassle, I wondered if I could overload the existing header field but I couldn't find a way.

Maybe we could have a separate meta field called headers that splits the result and appends --header to each.

[MikeMcQuaid]

Maybe we could have a separate meta field called headers that splits the result and appends --header to each.

We'll consider accepting a PR that implements this. Thanks!