Added compatibility with Laravel 9 and implemented some unit tests

[juanparati]

I changed the dependencies in order to provide compatibility with Laravel 9.

I also provided some basic unit tests.

The credentials for the unit test should be stored into tests/.secrets/config.json.

[jobbrown]

Thanks for this @juanparati.

@jimmyt2003 Can you review when you have time?

[jimmyt2003]

looks good

[samjonesigd]

@jobbrown @jimmyt2003 this okay to merge in? @McCaulay asked me last night as he's still getting notifications for this project