support RSASSA-PSS JWT signing algorithms (PS256,PS384,PS512)
added PSS token signing algorithms
fix OAuth 2.0 remote_user_claim comparison in server config merge

- use apr_strnatcmp on OAuth 2.0 remote_user_claim check instead of !=
- replace strcmp with apr_strnatcmp for string comparisons
- source code formatting
use DONE instead of HTTP error codes when writing HTML

terminate request processing without an error code after writing HTML
that is not related to (local) server errors
store response_type in state and make state a JSON object
verify at_hash and response_type

- verify at_hash value on "token id_token" implicit flow
- match authorization response against request type (code/id_token)