[BUG] An error is raised when openAPI variables used on server

[cbm-eheude]

Describe the bug
When I try to use this feature here an error is raised

To Reproduce
Steps to reproduce the behavior:
On serverless.doc.yml

documentation:
  version: 1.0.0
  description: 'My API description'
  servers:
    - url: https://my.{env}.url
      description: Dev & Staging server
      variables:
        env:
          enum:
            - dev
            - stage
          default: dev
    - url: https://my.url
      description: Production server
  ...

Expected behavior
Variables managed on servers

Desktop (please complete the following information):

• Serverless version: [e.g. 2.73.3]
• serverless-openapi-documenter version [e.g. 0.0.17]

Additional context
Add any other context about the problem here.
Possible solution
On createServers(servers) function add

if (server.variables) {
    obj.variables = server.variables
}

It is possible to do the same for authorization ?
https://swagger.io/specification/#security-scheme-object