doc: TCP Route + Demo

[draychev]

This GitHub issue is for fleshing out the OSM documentation around TCPRoute SMI policy and functionality:

• Document TCP Route and how OSM handles TCP traffic -- save the doc in ./docs/wip/tcp_traffic.md (exact location is TBD - wip short term)

  • Why is this needed? What scenarios does it enable? What are examples of these scenarios?
  • What does the SMI policy look like?
  • What would the resulting Envoy config look like?

• Create a small demo with sample apps and SMI showing how this feature works

• List Common Issues

  • What are the error messages when the destination service cannot be resolved?
  • What are the error messages when the source pod has no access to the destination pod?

• Create Troubleshooting Guide

  • What should we do if there's a DNS resolution error?
  • What should we do if there's no access to the remote service

• Automate Troubleshooting Guide in pkg/troubleshooter (create appropriate functions) - alternatively create a GitHub Issue with the stub of the function that could be eventually created within pkg/troubleshooter package to automatically troubleshoot this feature.

[zr-msft]

@draychev @phillipgibson this issue needs a demo to be completed

[phillipgibson]

@shashankram let me start on this.

[michelleN]

@phillipgibson are you still working on this? @jaellio can help if additional hands are needed

[shashankram]

I'll be looking into this.