"invalid algorithm specified" error when using a valid algorithm but a missing or invalid auth_jwt_key

[DevJake]

As per the title, if you use a valid algorithm - such as ES256 - but the auth_jwt_key value is missing or invalid, then you are presented with the error "invalid algorithm specified". Whilst the fix is clear, the error message itself is not intuitive and is misleading. I ended up digging through some issues and PRs just to confirm that ES256 is actually supported (it isn't listed in the README, just a heads up!).

If possible, some logic should be added to distinguish between an invalid algorithm and an invalid public key, so future users aren't equally stumped.

Many thanks!