fix(pricing): resolve in-partition Pricing region for AWS European Sovereign Cloud (aws-eusc)

[mlopezr]

fix(pricing): resolve in-partition Pricing region for AWS European Sovereign Cloud (aws-eusc)

Fixes / Description

On the European Sovereign Cloud region eusc-de-east-1, Karpenter's pricing
reconciler fails continuously with:

ERROR ... controller: providers.pricing ... Reconciler error ...
operation error Pricing: GetProducts, https response error StatusCode: 400,
api error UnrecognizedClientException: The security token included in the
request is invalid (aws-service-name=Pricing, aws-status-code=400)

Root cause

pkg/providers/pricing/pricing.go NewAPI selects the Pricing API region by
string-prefix matching the cluster region:

pricingAPIRegion := "us-east-1"
if strings.HasPrefix(cfg.Region, "ap-") {
    pricingAPIRegion = "ap-south-1"
} else if strings.HasPrefix(cfg.Region, "cn-") {
    pricingAPIRegion = "cn-northwest-1"
} else if strings.HasPrefix(cfg.Region, "eu-") {
    pricingAPIRegion = "eu-central-1"
}

eusc-de-east-1 starts with eusc-, not eu-, so it falls through to the
default us-east-1. Karpenter then signs the Pricing request for the commercial
aws partition while presenting an aws-eusc IAM token; the commercial
endpoint rejects the cross-partition token with 400 UnrecognizedClientException.

The Pricing API does exist in-partition at
api.pricing.eusc-de-east-1.amazonaws.eu — the bundled AWS SDK already knows
the aws-eusc partition and resolves it correctly once the region is right.

Fix

Add an eusc- branch mapping to eusc-de-east-1:

} else if strings.HasPrefix(cfg.Region, "eusc-") {
    pricingAPIRegion = "eusc-de-east-1"
}

Testing

Deployed Karpenter 1.14.0 into an EKS cluster in eusc-de-east-1 with no
AWS_ENDPOINT_URL_* overrides:

• Before this change: EC2/EKS/SSM/IAM/SQS all resolve natively (EC2NodeClass
  and NodePool reach Ready=True); only pricing errors with the 400 above.
• After this change: the pricing reconciler succeeds against
  api.pricing.eusc-de-east-1.amazonaws.eu.

This confirms the endpoint/partition support for the other services already
works via the vendored SDK — pricing's manual region-prefix table was the sole
remaining gap for aws-eusc.

Notes

• Consider also making the pricing reconciler degrade gracefully (as the
  existing us-gov skip does) when the Pricing API is unreachable in a given
  partition, so unknown future partitions log once rather than error-looping.

[joshuakguo]

lgtm

[mlopezr]

The two failing tests about LaunchTemplate Provider caching appear to be caused by an async-timing race.
In 1.30–1.33 + 1.35 all tests passed (a real regression would fail uniformly).
Could a maintainer please re-run the failed jobs? Thanks!