ElastiCache Emulator - Improve parameter groups, replication group metadata, tagging, and validation

[zyin-squareup]

Hey Nahuel,
I work with Ian and Jay, but with a focus on other datastores like elasticache. We are also using ministack to accelerate our integration testing and wanted to help improve the project.

Summary of the proposed changes:

Adds built-in ElastiCache default parameter groups for Redis, Memcached, and Valkey families, including cluster-mode .cluster.on variants.
Introduces explicit engine-version to parameter-group-family mapping so defaults use AWS-style names like default.redis7, default.redis6.x, default.redis5.0, and default.memcached1.6.
Makes seeded default parameter groups immutable by rejecting duplicate creates, deletes, modifies, and resets with AWS-shaped errors.
Expands replication group creation to materialize member cache clusters, populate richer metadata, preserve tags, expose member cluster IDs, and remove those member clusters on replication group deletion.
Adds create/modify replication group validation for missing user groups, returning UserGroupNotFound before mutating state or starting containers.
Adds replication group tag fanout so native ElastiCache tag updates and Resource Groups Tagging API updates propagate to member cluster ARNs.
Adds ElastiCache support to the Resource Groups Tagging API, including collection, resource validation, tag writes, removals, and resource type filtering.
Adds focused tests for parameter group defaults and immutability, user group validation, member cluster lifecycle, cluster-mode default groups, ElastiCache tagging, and Resource Groups Tagging API integration.

Link to the changes

ZiningYin@56a80db#diff-445892cd21ac9fa77b2a7845ae9ce8fb6d3b735058f59a616b1214bad960f8cd

[Nahuel990]

Hi @zyin-squareup awesome! Feel free to open an issue any time or tag me directly with @ We were already planning to add Valkey this week, but we've been busy...

The PR looks good overall. I don't know whether the UI is showing the __pycache__ changes because I'm looking at the raw diff, but those would be the only removals I'd suggest, along with the extra mount added in the Docker Compose file since we'd prefer to leave that at developer discretion.

On a separate note, the default-group list currently mixes names that are confirmed verbatim in AWS docs (default.redis7, default.redis6.x, default.redis5.0, default.valkey7/9, and the .cluster.on variants) with names where AWS docs only confirm the family (memcached1.6, valkey8, redis2.8). The default.<family> mapping is mostly convention-based.

If you have a source that explicitly lists default.memcached1.6, default.valkey8, or default.redis2.8, feel free to drop the link in the PR. Otherwise we'll treat those as best-effort mappings when we ship them

Also thanks for picking the tagging.py issue in the EC2 side!

[zyin-squareup]

Glad to help with this project. It is really awesome.
I will try to get an issue open for this next week and address the concerns you brought up. I have been swamped this week.