Support richer context in the BaseThing

Author: lu-zero

Thing.h

@@ -470,6 +470,7 @@ class ThingDevice {
   String id;
   String title;
   String description;
+  JsonObject context;
   const char **type;
 #if !defined(WITHOUT_WS) && (defined(ESP8266) || defined(ESP32))
   AsyncWebSocket *ws = nullptr;
@@ -484,6 +485,9 @@ class ThingDevice {
   ThingDevice(const char *_id, const char *_title, const char **_type)
       : id(_id), title(_title), type(_type) {}
 
+  ThingDevice(const char *_id, const char *_title, const char **_type, JsonObject _context)
+      : id(_id), title(_title), type(_type), context(_context) {}
+
   ~ThingDevice() {
 #if !defined(WITHOUT_WS) && (defined(ESP8266) || defined(ESP32))
     if (ws)
@@ -698,7 +702,11 @@ class ThingDevice {
   void serialize(JsonObject descr, String ip, uint16_t port) {
     descr["id"] = this->id;
     descr["title"] = this->title;
-    descr["@context"] = "https://webthings.io/schemas";
+    if (this->context) {
+        descr["@context"] = this->context;
+    } else {
+        descr["@context"] = "https://webthings.io/schemas";
+    }
 
     if (this->description != "") {
       descr["description"] = this->description;