weatherfeeder: split the former maximumdirect.net/weatherd project in two.

feedkit now contains a reusable core, while weatherfeeder is a concrete implementation that includes weather-specific functions.

internal/model/kind.go

@@ -0,0 +1,23 @@
+package model
+
+// Kind identifies which payload an Event carries.
+type Kind string
+
+const (
+	KindObservation Kind = "observation"
+	KindForecast    Kind = "forecast"
+	KindAlert       Kind = "alert"
+)
+
+// IsKnown returns true if k is one of the kinds supported by this binary.
+//
+// This is intentionally strict: if you add new kinds later, update this list.
+// That keeps validation useful (it catches partially-constructed events).
+func (k Kind) IsKnown() bool {
+	switch k {
+	case KindObservation, KindForecast, KindAlert:
+		return true
+	default:
+		return false
+	}
+}