feat: Allow setting state->open to unknown via DELETE

The schema defines the absence of state->open to represent the unknown
state. Previously it was not possible to explicitly set this state via
the HTTP endpoints.

types.SpaceAPIState.Open is now an enum which is either unknown, closed,
or open. Custom IsZero() and MarshalJSON() methods on the type ensure
marshaling the value yields a boolean for open/closed and an empty byte
slice for unknown (resulting in the field being absent from the final
response).

The handlers.StateOpenDELETE() function has been added to expose this
behavior.

Switching to encoding/json/v2 required raising the minimum Go version in
go.mod to 1.27.

Closes: CCCHH/spaceapid!37
Fixes:  CCCHH/spaceapid#38

persistence/persistentState.go

@@ -1,7 +1,8 @@
 package persistence
 
 import (
-	"encoding/json"
+	"encoding/json/jsontext"
+	"encoding/json/v2"
 	"errors"
 	"log"
 	"os"
@@ -20,7 +21,7 @@ func MergeOldState(response *types.SpaceAPIResponse) {
 	var (
 		err            error
 		oldState       []byte
-		persistedState types.PersistentSpaceState
+		persistedState types.PersistentState
 	)
 
 	log.Println("Merging old state from", persistentStatePath, "...")
@@ -87,27 +88,38 @@ func SaveCurrentState(response types.SpaceAPIResponse) {
 	defer file.Close()
 
 	// Create persistent state
-	persistentStateV14 := types.PersistentSpaceState{
-		State: struct {
-			Open       bool   `json:"open"`
-			LastChange int64  `json:"lastchange"`
-			Message    string `json:"message,omitempty"`
-		}{Open: response.State.Open, LastChange: response.State.LastChange, Message: response.State.Message},
+	var (
+		isOpen    bool
+		isUnknown bool
+	)
+	switch response.State.Open {
+	case types.SpaceAPIStateOpenIsUnknown:
+		isUnknown = true
+	case types.SpaceAPIStateOpenIsClosed:
+		break
+	case types.SpaceAPIStateOpenIsOpen:
+		isOpen = true
+	}
+	persistentState := types.PersistentState{
+		State: types.PersistentSpaceState{
+			Open: isOpen, IsUnknown: isUnknown,
+			LastChange: response.State.LastChange, Message: response.State.Message,
+		},
+		Sensors: make(map[string][]types.PersistentEnvironmentSensor),
 	}
 	// Save sensor state
-	persistentStateV14.Sensors = make(map[string][]types.PersistentEnvironmentSensor)
 	for key, environmentSensors := range response.Sensors {
-		persistentStateV14.Sensors[key] = make([]types.PersistentEnvironmentSensor, len(environmentSensors))
+		persistentState.Sensors[key] = make([]types.PersistentEnvironmentSensor, len(environmentSensors))
 		for i, sensor := range environmentSensors {
-			persistentStateV14.Sensors[key][i].Value = sensor.Value
-			persistentStateV14.Sensors[key][i].Location = sensor.Location
-			persistentStateV14.Sensors[key][i].Name = sensor.Name
-			persistentStateV14.Sensors[key][i].LastChange = sensor.LastChange
+			persistentState.Sensors[key][i].Value = sensor.Value
+			persistentState.Sensors[key][i].Location = sensor.Location
+			persistentState.Sensors[key][i].Name = sensor.Name
+			persistentState.Sensors[key][i].LastChange = sensor.LastChange
 		}
 	}
 
 	// Serialize persistent state
-	marshal, err := json.MarshalIndent(persistentStateV14, "", "\t")
+	marshal, err := json.Marshal(persistentState, json.JoinOptions(jsontext.Multiline(true), jsontext.SpaceAfterComma(true)))
 	if err != nil {
 		log.Fatalln("Failed serializing persistent state... error:", err)
 	}