feat(providers/aws): rich self-describing reservation names matching the Azure #686 format

[cristim]

Background

PR #686 adds a rich descriptive displayName for Azure reservation purchases (format {svc}-{region}-{sku}-{count}x-{term}-{paymt}-{ts}-{rand}), matching the operator-friendly shape of the existing AWS RDS purchase CSV's ReservationId column:

ri-cxm-trading-rds-aurora-mysql-ap-northeast-1-db-t4g-medium-1x-80pct-20260521-002019-227b6194

The AWS reservation purchase paths in providers/aws/services/*/client.go currently construct flat, low-signal IDs — e.g.:

// providers/aws/services/opensearch/client.go:161
reservationName = common.SanitizeReservationID(
    fmt.Sprintf("opensearch-%s-%d", rec.ResourceType, time.Now().Unix()),
    "opensearch-reserved-",
)

That yields opensearch-Standard_X-1779468234 — no region, no count, no term, no payment option, no human-readable timestamp. The same shape applies to the other AWS services that use IdempotentReservationID fallback or construct their own ID for Purchase* AWS SDK calls.

What to do

Extend the same rich-name pattern to AWS reservation purchases (5 services: rds, elasticache, memorydb, opensearch, redshift). Specifically:

1. Reservation-ID fallback strings in each AWS service client.go — when the idempotency token is empty / CLI-driven path. Currently:

   • rds, elasticache, memorydb, opensearch — fallback to <service>-<resourceType>-<unix> via SanitizeReservationID.
   • redshift — tag-guard, doesn't have a customer-supplied ID per se but writes a idempotency tag with similar metadata.

2. Tagging — for services that tag the purchased reservation (per feat(purchases): idempotent commitment creation (ClientToken/dedupe) to enable auto-re-drive of stranded approvals #636/feat(purchases): idempotent commitment creation (ClientToken/dedupe) (closes #636) #638/feat(purchases): make AWS RDS/ElastiCache/MemoryDB/OpenSearch/Redshift idempotent (refs #641) #652 idempotency work), include the same rich descriptors as tag values so the AWS console / CLI output is self-describing without cross-referencing CUDly's DB.

Proposed format

Match Azure's #686 format closely so the two sides are operationally symmetric:

{svc}-{region}-{sku}-{count}x-{term}-{paymt}-{ts}-{rand}

Where:

• svc (short code matching the AWS resource: rds, cache, memdb, opensearch, redshift)
• region: rec.Region (AWS regions are already conformant, e.g. us-east-1)
• sku: rec.ResourceType (db.t4g.medium, m5.large, etc.) — note dots become hyphens per AWS reservation-name allowlist; do this via SanitizeReservationID which already exists
• count: {rec.Count}x
• term: 1yr/3yr
• paymt: allup / noup / partup
• ts: YYYYMMDDhhmmss UTC compact
• rand: 8-hex from crypto/rand

Each AWS service has its own allowlist for reservation-name characters (RDS allows [a-zA-Z0-9-], ElastiCache similar, OpenSearch allows underscores, etc.) — defer to the existing common.SanitizeReservationID to enforce the union.

Implementation approach

Extract a shared builder in pkg/common/ (similar to where SanitizeReservationID lives), analogous to Azure's BuildDisplayName:

type ReservationNameFields struct {
    Service      string  // "rds", "cache", "memdb", "opensearch", "redshift"
    Region       string
    ResourceType string
    Count        int
    Term         string
    Payment      string
    Now          time.Time // injectable for tests
}

// BuildReservationName composes a rich, parseable identifier for an AWS
// reservation purchase. Matches the Azure DisplayName format from #686.
// Format: {svc}-{region}-{sku}-{count}x-{term}-{paymt}-{ts}-{rand}
//
// Pass the result through SanitizeReservationID for per-service allowlist
// compliance. Max length is constrained per the most-restrictive AWS API
// limit observed across the 5 services (verify before shipping —
// ReservationName for OpenSearch is up to 64 chars; ElastiCache's
// ReservedCacheNodeId allows up to 60).
func BuildReservationName(f ReservationNameFields) string { ... }

Then update each of the 5 service fallback paths to use it.

Tests

• New unit tests for BuildReservationName covering: happy path, worst-case length truncation, payment normalization, deterministic output given fixed Now + stubbed random.
• Per-service test extension: each service's existing reservation-name-construction test should assert the new shape (regex ^{svc-code}-) and that key fields (region, SKU, count) are present.

Acceptance criteria

• All 5 AWS service reservation-name fallback paths use the rich format.
• Operator opening the AWS console (or running aws rds describe-reserved-db-instances) sees an ID that encodes who/when/what without needing to query CUDly's DB.
• No regression in idempotency — same input + same IdempotencyToken still produces the same name (the token-based path bypasses the rich builder; the rich builder is for the no-token CLI fallback path only).
• Tags on Redshift (and any other tagging path added by feat(purchases): idempotent commitment creation (ClientToken/dedupe) to enable auto-re-drive of stranded approvals #636/feat(purchases): idempotent commitment creation (ClientToken/dedupe) (closes #636) #638/feat(purchases): make AWS RDS/ElastiCache/MemoryDB/OpenSearch/Redshift idempotent (refs #641) #652) include the rich descriptors.

Why this matters

Operators reading the AWS console see meaningless opensearch-Standard_X-1779468234 IDs today. After this lands, they see opensearch-us-east-1-r6gd_large_search-3x-1yr-allup-20260521T002019-a1b2c3d4 — instantly clear what was purchased, when, in which region, for how long. Symmetry with the Azure side (#686) means cross-cloud ops dashboards / runbooks can share parsing logic.

Related

• bug(providers/azure): displayName contains spaces — every Azure approve fails with DisplayNameInvalid #685 / fix(azure): sanitize Azure DisplayName to [A-Za-z0-9_-] for calculatePrice (closes #685) #686 (Azure rich displayName — the model)
• feat(purchases): idempotent commitment creation (ClientToken/dedupe) to enable auto-re-drive of stranded approvals #636 / feat(purchases): idempotent commitment creation (ClientToken/dedupe) (closes #636) #638 / feat(purchases): make AWS RDS/ElastiCache/MemoryDB/OpenSearch/Redshift idempotent (refs #641) #652 (AWS idempotency — sets the existing fallback-ID code path that this issue extends)