fix: php8.1 deprecation warnings

[SychO9]

Fixes #3383

Changes proposed in this pull request:

• Fixes the 4 instances of deprecations with PHP 8.1 on our codebase.
• I have forked axy/sourcemap and tobscure/json-api and updated them to support PHP 8.1
• The effect cannot be noticed until this is merged: Default to showing all PHP errors while providing ini input .github#7

Reviewers should focus on:
Do we want to move the newly forked packages under flarum ? the packages that needed forking and updating were: axy/sourcemap axy/errors axy/codecs-base64vlq and tobscure/json-api.

Necessity

• Has the problem that is being solved here been clearly explained?
• If applicable, have various options for solving this problem been considered?
• For core PRs, does this need to be in core, or could it be in an extension?
• Are we willing to maintain this for years / potentially forever?

Confirmed

• Frontend changes: tested on a local Flarum installation.
• Backend changes: tests are green (run composer test).
• Core developer confirmed locally this works as intended.
• Tests have been added, or are not appropriate here.

Required changes:

• Default to showing all PHP errors while providing ini input .github#7

[SychO9]

FYI sycho/json-api was forked from v0.4.1 of tobscure/json-api while we were using v0.3.0

[davwheat]

Is it worth opening PRs back to the original repos to see if maintainers would be willing to merge them instead of maintaining our own forks?

[SychO9]

That would be better tbh, I didn't try as axy/* packages looked abandoned. I'll give it a shot and see. Toby's package is confirmed abandoned so there's no need.

[davwheat]

Is it worth investigating whether to switch to Toby's new JSON API library for 2.0?

[SychO9]

That's seems to be the plan actually