Response Headers not displayed as part of Swagger UI

Description

We are using swagger code-gen to generate Jersey classes. Below are the issues:

i) ETag or response headers annotation are not getting added in the generated class.
II) Updated the api.mustache manually and got the annotation added in the generated class, but still the swagger ui is not showing the response headers.

Swagger-codegen version

3.0.0

Swagger declaration file content or url

Definition.yaml

responses:
        200:
          description: A list of policies
          content:
            application/vnd.asg-services-policy.v1+json:
              schema:
                $ref: '#/components/schemas/PoliciesDTO'
          headers:
            ETag:
              description: An ordered set of all policies versions
              schema:
                type: string

Steps to reproduce

We have added the below ETag in responses section and the same is not displayed, while loading swagger-UI. The ETag section is not displayed.

Related issues/PRs

Suggest a fix/enhancement

Expected Behavior : The swagger code-gen should generate the header annotations for jersey and Swagger UI also should display the Response headers.