normalizers: added a structure for normalizers; refactoring sources -> sources+normalizers is still todo.

internal/standards/schema.go

@@ -0,0 +1,20 @@
+package standards
+
+// Schema strings used by weatherfeeder.
+//
+// We standardize on schema matching for normalizers (rather than matching on
+// source names or kinds) because schema strings are explicit, versionable, and
+// independent of user configuration.
+//
+// Conventions:
+//   - Raw upstream payloads:  "raw.<provider>.<thing>.vN"
+//   - Canonical domain events: "weather.<kind>.vN"
+const (
+	// Raw upstream schemas (emitted by sources).
+	SchemaRawNWSObservationV1     = "raw.nws.observation.v1"
+	SchemaRawOpenMeteoCurrentV1   = "raw.openmeteo.current.v1"
+	SchemaRawOpenWeatherCurrentV1 = "raw.openweather.current.v1"
+
+	// Canonical domain schemas (emitted after normalization).
+	SchemaWeatherObservationV1 = "weather.observation.v1"
+)