Mark GrantedAuthority#getAuthority as @Nullable

[therepanic]

Since the GrantedAuthority#getAuthority contract itself implies that it can return null, we should mark it as @Nullable.

Closes: gh-17999

[therepanic]

Currently, the build crashes in the docs module, and it's not entirely clear why. Can you explain please why the build crashes in the following class test?

ObtainingMoreAuthorizationTests. profileWhenMissingAuthorityConfigurationThenRedirectsToAuthorizationServer()
ObtainingMoreAuthorizationTests. profileWhenMissingAuthorityConfigurationThenRedirectsToAuthorizationServer()

Note: Now it is fixed

[ronodhirSoumik]

Question :: though this implementation supports null case, but it is supposed to be avoided (as per the documentation -> returning null should be avoided unless actually required. ) So dont we losing the feature/control with the overall changes?
@therepanic @rwinch

[jzheaux]

@ronodhirSoumik, good question. The documentation also says that null "should be returned" in cases where it cannot be expressed with sufficient precision. In other words, returning null is recommended when needed.

[jzheaux]

Thanks, @therepanic! I've left some feedback inline.

[therepanic]

Thanks for the review, @jzheaux.

I agree with everything. It was a bad idea to mark authority as @Nullable when there was a simpler way to do it. I implemented this change as a separate commit to make it easier to read the changes.

I don't think the build crashes because of the changes in the PR.

[jzheaux]

Thanks, @therepanic! This is now merged into main