test: Update test coverage for tenant domain validation changes

[ramonschriks]

Changes

Added test coverage for previous added issuer claim validation with custom domain.

• Added expecting failure scenario with invalid domain not matching token issuer
• Added expecting failure scenario with invalid domain AND invalid custom domain not matching token issuer
• Added scenario with custom domain matching token issuer, should validate.
• Added scenario with custom domain not matching token issuer, should validate with tenant domain

References

Ref: https://github.com/auth0/auth0-PHP/pull/755

Contributor Checklist

• [x] I agree to adhere to the Auth0 General Contribution Guidelines.
• [x] I agree to uphold the Auth0 Code of Conduct.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (2dd8a74) 99.97% compared to head (f32478b) 100.00%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #756 +/- ## ============================================= + Coverage 99.97% 100.00% +0.02% Complexity 1383 1383 ============================================= Files 62 62 Lines 4781 4781 ============================================= + Hits 4780 4781 +1 + Misses 1 0 -1 ``` | [Flag](https://app.codecov.io/gh/auth0/auth0-PHP/pull/756/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | Coverage Δ | | |---|---|---| | [unittestsvalidate](https://app.codecov.io/gh/auth0/auth0-PHP/pull/756/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0) | `100.00% <100.00%> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=auth0#carryforward-flags-in-the-pull-request-comment) to find out more.

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