[Authorization] Evaluating a non-existent policy returns "false"

[leastprivilege]

When doing this:

if (await _authz.AuthorizeAsync(User, "does_not_exist"))

I get back false.

Doing the same in an Authorize attribute - it throws an exception.

[blowdart]

@HaoK can you slip this into beta8? I'd agree with throwing the exception in imperative checks too

[Tratcher]

No @blowdart, beta8 is 'done'.

[muratg]

Moving to RC1 per internal discussion.

[HaoK]

0eaec21