[HttpClient] Add HttpOptions->addHeader as a shortcut to add an header in an existing options object

[Dean151]

Q	A
Branch?	7.1
Bug fix?	no
New feature?	yes
Deprecations?	no
Issues
License	MIT

Currently, the HttpOptions object only provide a ->setHeaders option that override every existing headers. When we are provided an HttpOptions to customize a request, adding a request header requires to get the whole headers array, update it, and then set it back in the HttpOptions object. This DX improvement brings an addHeader option, allowing to add an header to the set without having to manage the existing ones.

When the header option is not yet provided, the ??= operator makes sure the headers is initialized with an empty array (PHP >= 7.4) When a header is already provided, it is overwritten.

[carsonbot]

Hey!

I see that this is your first PR. That is great! Welcome!

Symfony has a contribution guide which I suggest you to read.

In short:

• Always add tests
• Keep backward compatibility (see https://symfony.com/bc).
• Bug fixes must be submitted against the lowest maintained branch where they apply (see https://symfony.com/releases)
• Features and deprecations must be submitted against the 7.1 branch.

Review the GitHub status checks of your pull request and try to solve the reported issues. If some tests are failing, try to see if they are failing because of this change.

When two Symfony core team members approve this change, it will be merged and you will become an official Symfony contributor!
If this PR is merged in a lower version branch, it will be merged up to all maintained branches within a few days.

I am going to sit back now and wait for the reviews.

Cheers!

Carsonbot

[welcoMattic]

Thanks and congrats for your first contribution 👍

[fabpot]

Thank you @Dean151.