OpenAPI 3 oauth2 security scheme not applied globally for all endpoints

When providing an OpenAPI 3 security scheme, like

``` Groovy
openapi3 {
server = 'https://myserver.com/api'
title = 'My API'
description = 'My api description'
version = '0.5.0'
format = 'yaml'
oauth2SecuritySchemeDefinition = {
flows = ['authorizationCode']
tokenUrl = 'https://myauthserver.com/oauth/token'
authorizationUrl = 'https://myauthserver.com/authorize'
}
}
```

the `securitySchemes` is created correctly in the `openapi3.yaml`.

But to apply it to all endpoints, an additional (top-level) entry like

```
security:
- oauth2: []
```
would be needed.

I did not find a way to create this entry.