Symfony 5 support

[darthf1]

Changes

This PR adds support for Symfony 5. I only changed the version in composer.json.

Testing

Did some functional testing on my end, no additional entries in my log file and console. Seems to be working.

I did not add test coverage, since I have no experience on that topic. I was able to run the tests, and got the following:

HPUnit 5.7.27 by Sebastian Bergmann and contributors.

......EEE..E...EE........                                         25 / 25 (100%)

Time: 691 ms, Memory: 12.00MB

There were 6 errors:

1) Auth0\JWTAuthBundle\Tests\Security\Guard\JwtGuardAuthenticatorTest::testGetUserReturnsUnknownUserWhenJwtDecodingFails
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/Guard/JwtGuardAuthenticatorTest.php:105

2) Auth0\JWTAuthBundle\Tests\Security\Guard\JwtGuardAuthenticatorTest::testGetUserReturnsUserThroughLoadUserByJWT
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/Guard/JwtGuardAuthenticatorTest.php:140

3) Auth0\JWTAuthBundle\Tests\Security\Guard\JwtGuardAuthenticatorTest::testGetUserReturnsUserThroughLoadUserByUsername
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/Guard/JwtGuardAuthenticatorTest.php:172

4) Auth0\JWTAuthBundle\Tests\Security\Guard\JwtGuardAuthenticatorTest::testOnAuthenticationSuccess
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/Guard/JwtGuardAuthenticatorTest.php:230

5) Auth0\JWTAuthBundle\Tests\Security\JWTAuthenticatorTest::testTokenCreation
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/JWTAuthenticatorTest.php:26

6) Auth0\JWTAuthBundle\Tests\Security\JWTAuthenticatorTest::testNoAuthorization
Function ReflectionType::__toString() is deprecated

/srv/api/vendor/auth0/jwt-auth-bundle/Tests/Security/JWTAuthenticatorTest.php:51

ERRORS!
Tests: 25, Assertions: 34, Errors: 6.

[joshcanhelp]

Snyk passes locally:

❯ snyk test

Testing /Users/joshcanhelp/Sites/jwt-auth-bundle...

Organization:      auth0-sdks
Package manager:   composer
Target file:       composer.lock
Open source:       no
Project path:      /Users/josh-cunningham/Sites/jwt-auth-bundle
Licenses:          enabled

✓ Tested 35 dependencies for known issues, no vulnerable paths found.