[OBS-405]Add setup command for EC2 installation

[gmann42]

Why

• To onboard as many users as possible
• Current support is available only for Kubernetes, ECS but many of our users are running plain EC2

What

• Adds a new command postman-lc-agent setup for installation in linux servers

How

• After user runs setup
• Checks for Postman api key and collectionId existence
• Verifies api key has correct access permission
• setupAgentForServer -> checkUserPermissions -> checkSystemdExists -> configureSystemdFiles -> enablePostmanAgent -> postChecks

func configureSystemdFiles

• Read the env files as go template, fill in the api_key and collection id
• Check or create directories /etc/default and /usr/lib/systemd/system
• Over-write or create files /etc/default/postman-lc-agent and /usr/lib/systemd/system/postman-lc-agent.service

References

• Project Plan: https://postmanlabs.atlassian.net/wiki/spaces/PO/pages/4647125032/Linux+Server+Install
• Ticket: https://postmanlabs.atlassian.net/browse/OBS-405

Test plan

• collection Id missing, throw error collection missing
• POSTMAN_API_KEY missing, throw error api key missing
• Authorization/collection not existing in backend issues, throw incorrect api key error
• Non root user, throw error saying use root
• Systemd doesn't exist, throw error saying not supported yet
  TODO: Add more test cases

[mgritter]

Is this ready for final review, or still WIP?

[gmann42]

Is this ready for final review, or still WIP?

@mgritter This is ready for final review.

[mgritter]

The error messages here are all minimally informational to the end user. What are they supposed to do next?

Probably, contact the support email for most of them, but are there any that can be corrected?

[gmann42]

Yeah, I don't think user can do anything. because lack of systemd is quite unfixable.