Add support for allowing user to specify a delay between Notification and FIN for BGP Notification action.

[apratimmukherjee]

Feature Overview

• Related Issue: Fixes #461
• Brief Description:
  When Notifications and FIN are transmitted by an implementation very close to each other , some implementations can process the FIN early, resulting in information related to the Notification not being processed. This extra control allows the user to request for a delay between the two , which ensures the the device under test processes the Notification before the FIN arrives, closing the socket.

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Feature Details

• Redocly docs for this feature/branch

• New Locations/Nomenclature:
  New attribute fin_delay added for protocol.bgp.notification option in set_control_action

• Dev-Snappi branch reference

• Example command to fetch the dev-snappi branch:

  go get github.com/open-traffic-generator/snappi/gosnappi@bgp_notf_fin_delay
  

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Code snippets

Please provide a concise, well-commented code snippet demonstrating how to use the new feature in snappi/gosnappi:
The snippet should we within

....
ceaseAction := gosnappi.NewControlAction()
ceaseAction.Protocol().Bgp().Notification().
               SetNames([]string{"BGP4.peer"}).
               Custom().SetCode(6).SetSubcode(6).
               SetFinDelay(1000) // wait for one second before tearing down connection.

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Test Specification (Optional)

• Example test scenario:
  • Configuration details: Test Port - DUT
    • Create and bring up BGP session
    • Send trigger Notification with delay to ensure DUT receives the Notification before processing the FIN.
    • Retrieve Notification cause from DUT via telemetry