OBS-393 Simplify user interface for ECS installation

[gmann42]

Why ?

• Started with bugs raised from user https://postman.slack.com/archives/C05SCB5LA6R/p1695341965693699?thread_ts=1695339771.750859&cid=C05SCB5LA6R
  https://postman.slack.com/archives/C05SEPAHY1Z/p1695339058308279

What

• Removes interactiveness from ECS cli
  New Usage

POSTMAN_API_KEY=<postman-api-key> postman-lc-agent ecs add \
--collection <postman-collectionID> \
--region <aws-region> \
--cluster <full ARN of ECS cluster> \
--service <full ARN of ECS service>

• Deletes un-used code listECSClusters, listTasks, ListServices etc.
• Adds README.md for usage.

How

• User inputs aws region, full ARN of cluster and service
• Load profile AWS credentials
• DescribeCluster to verify existence and get cluster name
• DescribeService to verify existence and get TaskDefinitonARN
• TaskDefinitonARN fetched is then used to describeTask
• modifyTask use RegisterTask to create a new definition with postman-lc-agent container as the side car
• updateService udpates the ECS service with new task definition

Ticket link: https://postmanlabs.atlassian.net/browse/OBS-393

• Discussion for change of interface: https://postman.slack.com/archives/C05FP23TG02/p1695395401432759?thread_ts=1695340195.832369&cid=C05FP23TG02

[mgritter]

Dereference without checking nil, what if there is no task registered yet?

[gmann42]

A service can not be created without a task, we are fetching the service from AWS and using it's output to pick the taskARN

[mgritter]

You removed %d but kept it in the parameter list. We should specify the version number if it is still possible to do so.

[gmann42]

AWS auto-increments the revision numbers, we can't just do current + 1.

Revisions    Status
1                    Active
2                    Active
3                   Deployed in service
4                   Active
5                   Inactive(or even deleted aws remembers the highest count always)

New task definition revision will be 6, +1 would show incorrect value of 4.
For my testing i had deleted or marked inactive bunch of times, it always remembers the last highest + 1.
So this is not reliable without some sort of hack

[mgritter]

OK, good point. Do we show the revision number of our modified task anywhere in our output?