Override description from operation template

[pshao25]

Currently when we use a template, e.g., ArmResourceRead, its responses have its own description like

"responses": {
  "200": {
    "description": "Azure operation completed successfully.",
    "schema": {
      "$ref": "#/definitions/EmployeeListResult"
    }
  },
  "default": {
    "description": "An unexpected error response.",
    "schema": {
      "$ref": "../../../common-types/resource-management/v5/types.json#/definitions/ErrorResponse"
    }
  }
}

But brownfield service defined its own description. We should have a way to override these descriptions.

[markcowl]

@pshao25 We should not try to match the response description for existing swaggers. This should be a non-goal. Descriptions of response models make sense, but the descriptions of response status codes in swagger are of limited value.

If there is a need in some very strange case to do this, you can use the Response parameter in each operation template to replace the responses and add your own documentation like this

But again matching the description of the status code responses in swagger should be an explicit non-goal of conversion