[BUG][javascript client] Server Object without enum not considered

Created by: jdorel

Description

https://github.com/OpenAPITools/openapi-generator/blob/8e91b8c62a1710ae4924b9c5f931c549f40d4e5a/modules/openapi-generator/src/main/resources/Javascript/es6/ApiClient.mustache#L648

If an enum_values is not specified, it is impossible to modify the value.

The specification (see the exemple just above the link) indicates that without any enum, any value should be accepted.

openapi-generator version

4.0.0-beta3