Make compatible with PHP 8.4

[ruudk]

League\OAuth2\Client\Provider\AbstractProvider::authorize(): Implicitly marking parameter $redirectHandler as nullable is deprecated, the explicit nullable type must be used instead

When #1033 is merged, I will propose a PR to add PHP 8.4 to the matrix as well.

[ruudk]

@ramsey Could you please approve the workflow?

[carloscz]

hi, running our internal PHP 8.4 compatibility checks and this abstract library emits a lot of deprecations for us so thank You very much for this PR :) is there any timeframe for release?

[ruudk]

@shadowhand Would you be able to help out?

[stephanvierkant]

https://github.com/hwi/HWIOAuthBundle looks unmaintained so I'm looking for an alternative, but this repo looks unmaintained as well :(

[ruudk]

I decided to remove this dependency and do the OAuth dance with Google myself. Wasn't that hard.

[carloscz]

yeah, we probably will switch to JWT parsing and signature checking on backend only as well if this doesn't get pulled through

[ramsey]

I approved the workflow, but now there are a bunch of failures that appear unrelated to your change. I'll need to investigate and fix these.

[stephanvierkant]

Let's remove all unsuppported versions (<8.1), to make it easier.