OAuthSignupNotSupportedException
class OAuthSignupNotSupportedException(val authServerUrl: String, val advertisedPromptValues: List<String>) : RuntimeException
Thrown by AtOAuth.beginSignup when the configured authorization server's /.well-known/oauth-authorization-server metadata does not advertise "create" in prompt_values_supported. Per OIDC Prompt Create 1.0 the prompt=create value tells the server "render the signup UI"; servers that don't advertise the value may silently ignore it or reject the PAR.
Consumers targeting non-conformant entryways can bypass the check via beginSignup(authServer, requirePromptCreateSupport = false).