Make the onEventReceived type more explicit

NightLight.Core/Core.fs

@@ -22,15 +22,17 @@ type Event =
     | ReceivedZigbeeEvent of payload: string
     | TimeChanged of DateTime
 
+type ParseEventError = ParseZigbeeEventError of ParseZigbeeEventError
+
 type State = { Time: DateTime }
 
-let onEventReceived (state: State) (event: Event) =
+let onEventReceived (state: State) (event: Event) : Result<State * ZigbeeCommand seq, ParseEventError> =
     result {
         let partOfDay = getPartOfDay state.Time
 
         match event with
         | ReceivedZigbeeEvent payload ->
-            let! zigbeeEvent = parseZigbeeEvent payload
+            let! zigbeeEvent = parseZigbeeEvent payload |> Result.mapError ParseZigbeeEventError
 
             return
                 state,

NightLight/Program.fs

@@ -44,7 +44,7 @@ let private handleEvent (mqttClient: IMqttClient) (logger: ILogger) (state: Stat
             do! publishZigbeeCommands mqttClient logger commands
             return newState
         }
-    | Error UnknownType -> async.Return state
+    | Error(ParseZigbeeEventError UnknownType) -> async.Return state
     | Error e ->
         logger.LogError("Error {Error} while {Event}", e, event)
         async.Return state