feat: Add support for PHP 8.1, 8.2

[dplewis]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

Migrate TravisCI to Github Actions

Closes: #479, #488

Approach

• Support PHP 8.1, 8.2
• Drop support for <= 8.0
• Remove travis
• Bump composer packages
• Remove mailgun adapter
• Remove warnings
• Remove deprecation warnings
• Support for Parse Server 6
• Fix flaky tests
• Add documentation deployment

TODOs before merging

• Add tests
• Add changes to documentation (guides, repository pages, in-code descriptions)
• Add changelog entry

[parse-github-assistant]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.20 ⚠️

Comparison is base (184460b) 98.07% compared to head (86df298) 97.88%.

❗ Current head 86df298 differs from pull request most recent head 57b8d4f. Consider uploading reports for the commit 57b8d4f to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #489      +/-   ##
============================================
- Coverage     98.07%   97.88%   -0.20%     
- Complexity     1063     1066       +3     
============================================
  Files            39       39              
  Lines          2964     3262     +298     
============================================
+ Hits           2907     3193     +286     
- Misses           57       69      +12     

Impacted Files	Coverage Δ
src/Parse/ParseUser.php	98.40% <ø> (+0.09%)	⬆️
src/Parse/HttpClients/ParseCurlHttpClient.php	95.50% <100.00%> (+0.15%)	⬆️
src/Parse/HttpClients/ParseStreamHttpClient.php	96.10% <100.00%> (-2.53%)	⬇️
src/Parse/ParseACL.php	100.00% <100.00%> (ø)
src/Parse/ParseQuery.php	99.52% <100.00%> (-0.24%)	⬇️

... and 18 files with indirect coverage changes

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[mtrezza]

Great work!

[mtrezza]

See #489 (comment)

[mtrezza]

Changed this PR to feat since it changes the supported PHP versions and is therefore a breaking change.

[mtrezza]

Looks good! Thanks for this PR, let's hope it motivates others to bring this SDK up-to-date.

[mtrezza]

@dplewis Do you remember how to prepare and publish a release in this repo?

Past commits to prepare releases only contain the changelog entry and bumping the internal client version that is sent to Parse Server in ParseClient.php.

For example fa132ca

We don't have auto-release in this repo yet. To add that, I'd like to understand the steps needed to publish it manually.

[dplewis]

@mtrezza I have absolutely no idea how to publish this or how it works. I just do a tag and release and it magically publishes. @montymxb @acinader handled releases So they might know

[mtrezza]

I've opened #492 to find out more about release publishing.