v2.0.0

Updated the default parameter to align with the latest Redis engine version. @tatematsu-k (#272)

## what

• Updated the default parameter to align with the latest Redis engine version.

why

• According to the official AWS announcement, Redis v4 will reach the end of standard support by the end of January 2026.
• Since there is no practical reason to create new Redis clusters with v4 at this point, the default should be set to the latest version.
• For environments that intentionally use older versions and prefer not to upgrade automatically, it is recommended to override the version explicitly via parameters.

references

• https://aws.amazon.com/about-aws/whats-new/2025/07/amazon-elasticache-extended-redis/?nc1=h_ls

docs: snapshot_retention_limit determines if Backup is enabled @oycyc (#270)

https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/elasticache_replication_group#snapshot_retention_limit-1

snapshot_retention_limit determines whether or not backup is enabled. Good for documentation here.