[Enhancement]: Deprecate uppercase versions of `engine` attribute in `elasticache` resource types

[gdavison]

Description

A number of resource types in elasticache support both uppercase and lowercase versions of the engine attribute. Update them to standardize on the default lowercase. This will eventually allow removing diff suppression from the attribute.

Add deprecation warnings for uppercase values.

Affected Resource(s) and/or Data Source(s)

• aws_elasticache_replication_group
• aws_elasticache_serverless_cache
• aws_elasticache_user
• aws_elasticache_user_group

Potential Terraform Configuration

No response

References

No response

Would you like to implement a fix?

None

[github-actions]

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[jar-b]

Breaking down the current state of case sensitivity and suppression functions in impacted resources. In order to be in-scope, the arguments validation must allow case insensitive values and include a diff suppression function.

Resource	Case Insensitive	Diff Suppression	In-Scope
aws_elasticache_cluster 1	No	No	No
aws_elasticache_replication_group 2	Yes	No	No
aws_elasticache_serverless_cache 3	N/A (no validation at all)	No	No
aws_elasticache_user 4	Yes	Yes	Yes
aws_elasticache_user_group 5	Yes	Yes	Yes

[jar-b]

Closed via #42419. These changes will be available in the v6.0.0 beta release later this month.

[github-actions]

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[github-actions]

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