Add a new field to the alert schema to fix a mismatch between the prior schema and the upstream NWS API

model/alert.go

@@ -55,9 +55,11 @@ type WeatherAlert struct {
 	Instruction string `json:"instruction,omitempty"`
 
 	// Timing (all optional; provider-dependent).
+	// Onset and Ends describe the alert period. Expires is provider expiration metadata.
 	Sent      *time.Time `json:"sent,omitempty"`
 	Effective *time.Time `json:"effective,omitempty"`
 	Onset     *time.Time `json:"onset,omitempty"`
+	Ends      *time.Time `json:"ends,omitempty"`
 	Expires   *time.Time `json:"expires,omitempty"`
 
 	// Scope / affected area.