[5.x] Add --header option to static warm command

[ChristianPraiss]

Add support for custom headers in static:warm command

This PR introduces a new --headers option to the static:warm command, allowing users to specify custom HTTP headers for requests made during cache warming, e.g. for:

• Pages requiring authentication or API tokens for access.
• Need to trigger static cache refreshes even when static files are being served, using custom server rules. Especially useful for zero-cache-downtime scenarios

Related docs here: statamic/docs#1674

[jasonvarga]

Thank you for the PR.

The test was nice, thanks! But there was a false positive.

Since you can't pass an array from the CLI (but you can in the test), you need to use the option multiple times as you noted. But, you need to define it in the signature with an asterisk. Running the command from the CLI the way you had it only used the first one you passed in.

Also, since you need to use the option multiple times, and each time it's a singular header, I've changed the option from headers to header.

please static:warm --header="Foo: Bar" --header="Bar: Baz"

[ChristianPraiss]

Always happy to help!

Good to know that, thx for noticing and fixing it right away! The intricacies of artisan commands...