feat(supported-version): add service_preferences and support for php-fpm and nginx (#255)

supported-version/src/services/preferences/tier-map.ts

@@ -0,0 +1,63 @@
+/**
+ * A category of services that Magento can choose between. Each tier
+ * has one or more concrete implementations (e.g. the `search` tier
+ * resolves to either `opensearch` or `elasticsearch`).
+ */
+export type Tier = 'db' | 'search' | 'queue' | 'cache';
+
+/**
+ * Caller-expressed preference of "which implementation to use for which tier."
+ * Produced by `parseServicePreferences` from the `service_preferences`
+ * action input, then threaded into `buildServicesForEntry` to override
+ * the per-tier default pick. Partial because callers only need to name
+ * the tiers they care about; unset tiers fall back to the version's
+ * default implementation.
+ */
+export type ServicePreferences = Partial<Record<Tier, string>>;
+
+/**
+ * Reverse lookup: which tier does each known service implementation
+ * belong to. The keys of this map define the closed set of legal
+ * service names in `service_preferences`; anything not listed here is
+ * rejected as an unknown service. nginx and php-fpm are intentionally
+ * absent — they're complementary (the `web` tier emits both together),
+ * not alternatives, so picking one via preferences would be meaningless.
+ */
+export const SERVICE_TIER_MAP: Record<string, Tier> = {
+  mysql: 'db',
+  elasticsearch: 'search',
+  opensearch: 'search',
+  rabbitmq: 'queue',
+  redis: 'cache',
+  valkey: 'cache',
+};
+
+/**
+ * Forward lookup: the implementations available within each tier,
+ * ordered by default preference (first entry wins when no caller
+ * preference is supplied). Used by the validator to render
+ * "supported: a, b" lists in compatibility errors and by
+ * `buildServicesForEntry` to know what to fall back to.
+ */
+export const TIER_IMPLEMENTATIONS: Record<Tier, string[]> = {
+  db: ['mysql'],
+  search: ['opensearch', 'elasticsearch'],
+  queue: ['rabbitmq'],
+  cache: ['valkey', 'redis'],
+};
+
+/**
+ * Flat list of every legal service name in `service_preferences`.
+ * Surfaced in unknown-service error messages so the caller sees
+ * exactly what's accepted without having to read source.
+ */
+export const KNOWN_SERVICE_NAMES = Object.keys(SERVICE_TIER_MAP);
+
+/**
+ * Returns the tier a service name belongs to, or `undefined` if the
+ * name isn't recognized. Callers use the undefined return as the
+ * signal to reject the input as unknown.
+ */
+export const tierFor = (serviceName: string): Tier | undefined => {
+  return SERVICE_TIER_MAP[serviceName];
+}