Adds tests to cover policy overrides and when authorize is called in other namespaces

[TheDevJoao]

This PR adds more tests as suggested in this comment from the issue #723

To do

• [X] I have read the contributing guidelines.
• [X] I have added relevant tests.
• [X] No documentation alterations required.
• [X] I have made sure the individual commits are meaningful.
• [X] I have added relevant lines to the CHANGELOG.

PS: Thank you for contributing to Pundit ❤️

[TheDevJoao]

Hey @dgmstuart, could you check this out in the near future? I'd appreciate any feedback, thanks! 😄

[TheDevJoao]

@dgmstuart Any updates on this PR?