Allow configuring the base server

Making requests on CRM throws the following errors:

{
  "title":"OpenApiValidationError",
  "message":"Your request could not be validated against the openapi specification.",
  "data":[
    {
      "exception":"ServerNotFound",
      "message":"Server not found for https://intranet.logilab.fr/crm/api/v1/schema"
    }
  ]
  }