Allow user to override getToken function.

[TheCynosure]

Description

Allows the user to specify a custom function for retrieving the authorization token. Currently, the getToken function is fixed and the user is only able to use one of the pre-determined locations for their authorization tokens, such as the Authorization header.

Now the developer can specify whatever location they desire. This is asked for in #147 and I need this as well.

This should not be a breaking change. I also tried to pass the opts object into the existing getToken function, but this approach seems the least intrusive and most configurable.

References

#147

Testing

Unit tests were added for this functionality. Should be verifiable with npm test. Tested on NodeJS v18.19.1, Ubuntu 24.04.

• This change adds test coverage for new/changed/fixed functionality

Documentation

Documentation was updated with npm run docs, it led to more changes than I expected, but it seems to be from a commit hash reference changing.

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 the default branch