Add C++-style guard class for JSON Buffer lock

Add JSONBufferGuard, an RAII lock guard class for JSONBufferLock
analogous to std::lock_guard.  This permits binding the guard to a scope,
such as an object life cycle or function body, guaranteeing that the
lock will be released when the scope exits.

wled00/fcn_declare.h

@@ -360,6 +360,22 @@ um_data_t* simulateSound(uint8_t simulationId);
 void enumerateLedmaps();
 uint8_t get_random_wheel_index(uint8_t pos);
 
+// RAII guard class for the JSON Buffer lock
+// Modeled after std::lock_guard
+class JSONBufferGuard {
+  bool holding_lock;
+  public:
+    inline JSONBufferGuard(uint8_t module=255) : holding_lock(requestJSONBufferLock(module)) {};
+    inline ~JSONBufferGuard() { if (holding_lock) releaseJSONBufferLock(); };
+    inline JSONBufferGuard(const JSONBufferGuard&) = delete; // Noncopyable
+    inline JSONBufferGuard& operator=(const JSONBufferGuard&) = delete;
+    inline JSONBufferGuard(JSONBufferGuard&& r) : holding_lock(r.holding_lock) { r.holding_lock = false; };  // but movable
+    inline JSONBufferGuard& operator=(JSONBufferGuard&& r) { holding_lock |= r.holding_lock; r.holding_lock = false; return *this; };
+    inline bool owns_lock() const { return holding_lock; }
+    explicit inline operator bool() const { return owns_lock(); };
+    inline void release() { if (holding_lock) releaseJSONBufferLock(); holding_lock = false; }
+};
+
 #ifdef WLED_ADD_EEPROM_SUPPORT
 //wled_eeprom.cpp
 void applyMacro(byte index);