open fun getAllFileExtensions(): MutableList<String>
{@inheritDoc}
At startup this method returns extensions explicitly registered with either PathExtensionContentNegotiationStrategy or ParameterContentNegotiationStrategy. At runtime if there is a "path extension" strategy and its useRegisteredExtensionsOnly property is set to "false", the list of extensions may increase as file extensions are resolved via org.springframework.http.MediaTypeFactory and cached.