feat(elasticache/serverless): Add endpoint and reader_endpoint connec…

[portswigger-tim]

…tionDetails

Description of your changes

Adds connection details for ServerlessCache instances.

Fixes #1568

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

[turkenf]

/test-examples="examples/elasticache/v1beta1/serverlesscache.yaml"

[portswigger-tim]

Here are some references to make help make sure that I got this correct:

• Terraform attribute reference: https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/elasticache_serverless_cache#endpoint-block

• Implementation inspired by the almost identical memorydb config: https://github.com/crossplane-contrib/provider-upjet-aws/blob/main/config/memorydb/config.go#L18-L33

[turkenf]

Thank you for your effort in this PR @portswigger-tim. Could you please test the resource manually and verify that the connection keys and values ​​​​are coming to the secret correctly? It would be great if you could add the results to the PR description.

[portswigger-tim]

Close, but not quite:

Name:         platform-valkey-redis
Namespace:    platform
Labels:       <none>
Annotations:  <none>

Type:  connection.crossplane.io/v1alpha1

Data
====
endpoint_0_address:         64 bytes
reader_endpoint_0_address:  64 bytes

I'm guessing that the type is not quite right on the port.