feat(platform): summarize missing vehicle sources

vehicle-data-platform/apps/api/internal/platform/model.go

@@ -147,6 +147,7 @@ type VehicleServiceSummary struct {
 	IdentityRequiredVehicles int                 `json:"identityRequiredVehicles"`
 	ServiceStatuses          []ServiceStatusStat `json:"serviceStatuses"`
 	Protocols                []ProtocolStat      `json:"protocols"`
+	MissingSources           []MissingSourceStat `json:"missingSources"`
 }
 
 type VehicleServiceStatus struct {
@@ -158,6 +159,11 @@ type VehicleServiceStatus struct {
 	OnlineSourceCount int    `json:"onlineSourceCount"`
 }
 
+type MissingSourceStat struct {
+	Protocol string `json:"protocol"`
+	Count    int    `json:"count"`
+}
+
 type VehicleSourceStatus struct {
 	Protocol    string `json:"protocol"`
 	Online      bool   `json:"online"`