Add Summaries to Plan And Apply PR Comments

[X-Guardian]

Community Note

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• I'd be willing to implement this feature (contributing guide)

Describe the user story

As an Atlantis user, I would like to see the following:

1. If there is more than 1 project in a plan, when the plan is finished, I would like to be able to quickly see how many projects have changes, have no changes and have failed the plan.
2. If there is more than 1 project in an apply, when the apply is finished, I would like to be able to quickly see how many projects applied successfully, how many failed and how many errored.

Describe the solution you'd like

Add summary lines to the Atlantis plan and apply PR comments detailing the required information.

Describe the drawbacks of your solution

None

Describe alternatives you've considered

None