[FEATURE REQUEST]: citrixadc_responderaction - headers support

[adc-nerd]

Description

It's possible to send custom headers in a "responder action" i.e cache-control for maintenance pages.
This is currently not implemented in "citrixadc_responderaction".

Affected Resource(s) and/or Data Source(s)

citrixadc_responderaction

Equivalent NetScaler CLI Command

add responder action res_act_maintenance_page respondwithhtmlpage my-html-page responseStatusCode 503 -headers cache-control("no-cache,no-store,must-revalidate")

Potential Terraform Configuration

resource "citrixadc_responderaction" "my-html-page" {
...
headers = "cache-control(\"no-cache,no-store,must-revalidate\")"
...
}

References

API Docs: https://developer-docs.netscaler.com/en-us/adc-nitro-api/current-release/configuration/responder/responderaction