Add static analysis

[FrontEndCoffee]

Description

There are no source code changes in this PR.

PHPStan is a static analysis tool for PHP. By adding this tool to the project, a quality standard of code can be maintained over time automatically.

Currently, the configured level of strictness is configured to 1 (see phpstan.neon). This can be increased all the way to 8. I suggest making these increments a PR at the time, as some code will need to be fixed to get to those levels.

I also suggest in time adding the following plugins to the PHPStan configuration:

• phpstan/phpstan-deprecation-rules
• phpstan/phpstan-strict-rules

As you can see, I have also updated the circle-ci config to include this tool in to the CI flow.

Testing

You can manually run PHPStan by executing composer static-analysis

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not master

[FrontEndCoffee]

@evansims The CI seems to fail on deprecation notices. I am not sure why master does not fail on this.

1) Auth0\Tests\unit\Auth0Test::testThatExchangeFailsWithNoStoredNonce
The use of the method "withClaim" is deprecated for registered claims. Please use dedicated method instead.

I do see that there are quite some deprecation notices in the application, shall I fix them as part of this PR?

[evansims]

Hey @FrontEndCoffee 👋 This is great, thanks so much for your pull request! Adding this had been on my backlog and I really appreciate you taking it on here. Don't fret too much on the CI issues, those will clear up once #467 is merged, and we'll get your PR merged in at that point.

Just waiting on our internal review process to finish on 467 and we can move forward, but with the holidays things are moving a bit slower than usual right now.

[evansims]

Looks great, thank you again for your contribution on this 👍

[github-actions]

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