adapter:outbound:notification — notification adapter

Registered identity

Module ID: adapter-outbound-notification
Gradle path: :adapter:outbound:notification
Focused test (derived from Gradle path): ./gradlew :adapter:outbound:notification:test --console=plain
Runtime baseline: Java 21; repository framework baseline: Spring Boot 4.0.0.
Registry SSOT: src/config/architecture/modules.json.

Package root: dev.caskeleton.adapter.outbound.notification.

Preserve the current raw notification router/provider seams only as the R0 legacy compatibility baseline until the reviewed canonical cutover removes them.
Implement future provider protocols behind application-owned ports without leaking SDK, transport, bootstrap, or persistence types.
Own provider settings, technical fallback mechanics, and provider adaptation; application policy owns mode, eligibility, retry/fallback decisions and business failure semantics.
Reuse adapter:outbound:support for shared outbound concerns.

RoutingNotifier performs route-list fan-out over (Channel, providerId).
FailOpenNotificationProvider applies one global fail-open rule.
google-email/GoogleEmailClient and slack-webhook/SlackClient are fake-only extension seams, not production integrations or qualified provider cards.
Checked-in provider selector keys drift from the router's routes + provider enabled grammar. Preserve and document that drift until the canonical graph replaces it; do not silently reinterpret the old keys.
There are no feature/application production consumers and no real-provider, durable, receipt, security, load, or rotation evidence.
The exact legacy deletion inventory lives in README.md. Do not add behavior to those classes while building their canonical replacements.

Allowed dependency edges come only from the module's src/config/architecture/modules.json entry.
No inbound DTO/controller, persistence, bootstrap, or sample dependency.
Provider selection may route configured channels but must not encode business eligibility rules.

Use provider/client fakes and contract tests; no real webhook or email network calls. Settings changes include binding/validation tests.