feat(ecs): warning when creating a service with the default minHealthyPercent

[MarrickLip]

Issue

Closes #31705

Reason for this change

CDK overrides the default value of 100% used by CloudFormation's AWS::ECS::Service and the CreateService API. This allows the number of running tasks to drop by up to 50% during deployments and Fargate maintenance etc.

This is an unsafe default for services which must support a consistent load e.g. handle web traffic via an ALB.

Description of changes

A warning appears when the default value is implicitly used. CloudFormation's default is overridden in three different places so multiple warnings are added:

• BaseService emits @aws-cdk/aws-ecs:minHealthyPercent when minHealthyPercent is undefined
• Ec2Service emits @aws-cdk/aws-ecs:minHealthyPercentDaemon when daemon is true and minHealthyPercent is undefined
• ExternalService emits @aws-cdk/aws-ecs:minHealthyPercentExternal when minHealthyPercent is undefined

At most one warning appears due to the way the CloudFormation's default is overidden.

README.md has been updated for aws_ecs and aws_ecs_patterns to ensure these examples don't trigger this warning.

Description of how you validated changes

Unit tests have been added to ensure the warnings appear are there when they should be and not when they shouldn't.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

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[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 6af52c8
• Result: SUCCEEDED
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[MarrickLip]

The pull request linter fails with the following errors:

❌ Features must contain a change to an integration test file and the resulting snapshot.

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Exemption Request: warning doesn't change synthesized CloudFormation stacks so new integration tests not required.

[aws-cdk-automation]

The pull request linter fails with the following errors:

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[aws-cdk-automation]

The pull request linter fails with the following errors:

❌ Features must contain a change to an integration test file and the resulting snapshot.

PRs must pass status checks before we can provide a meaningful review.

If you would like to request an exemption from the status checks or clarification on feedback, please leave a comment on this PR containing Exemption Request and/or Clarification Request.

✅ A exemption request has been requested. Please wait for a maintainer's review.