Enum case always in uppercase when converted in SDL

[madolala]

Describe the bug
I found that the enums cases appears always in uppercase on SDL generated from Json openApis.

To Reproduce
Steps to reproduce the behavior:

1. With the CLI : 'openapi-to-graphql oas.json --save schema.graphql' with lowercases enum in your oas
2. Check the concerned enum in schema.graphql
3. See that it's in upper

Expected behavior
Enum that respect cases

[MattBodey]

I'm also experiencing this, even when using the --simpleNames option