Made WebServer more reusable

Only non-general (non-reusable) part of WebServer was the device reboot after the submitted configuration had been stored.
Removed this from the WebServer and added it (via a function reference call) to Basecamp.

Added a reset function, which clears all interface elements such that new elemets can be added at will.
The reset function can be used if the web server should be reconfigured during runtime. But it might not work yet.

Basecamp.cpp

@@ -192,7 +192,11 @@ bool Basecamp::begin(String fixedWiFiApEncryptionPassword)
 	if (shouldEnableConfigWebserver())
 	{
 		// Start webserver and pass the configuration object to it
-		web.begin(configuration);
+		// Also pass a Lambda-function that restarts the device after the configuration has been saved.
+		web.begin(configuration, [](){
+			delay(2000);
+			esp_restart();
+		});
 		// Add a webinterface element for the h1 that contains the device name. It is a child of the #wrapper-element.
 		web.addInterfaceElement("heading", "h1", "","#wrapper");
 		web.setInterfaceElementAttribute("heading", "class", "fat-border");

WebServer.cpp

@@ -26,7 +26,7 @@ WebServer::WebServer()
 #endif
 }
 
-void WebServer::begin(Configuration &configuration) {
+void WebServer::begin(Configuration &configuration, std::function<void()> submitFunc) {
 	SPIFFS.begin();
 
 	server.on("/" , HTTP_GET, [](AsyncWebServerRequest * request)
@@ -98,7 +98,7 @@ void WebServer::begin(Configuration &configuration) {
 			request->send(response);
 	});
 
-	server.on("/submitconfig", HTTP_POST, [&configuration, this](AsyncWebServerRequest *request)
+	server.on("/submitconfig", HTTP_POST, [&configuration, submitFunc, this](AsyncWebServerRequest *request)
 	{
 			if (request->params() == 0) {
 				DEBUG_PRINTLN("Refusing to take over an empty configuration submission.");
@@ -119,9 +119,8 @@ void WebServer::begin(Configuration &configuration) {
 			configuration.save();
 			request->send(201);
 
-			// Why? What is this magic value for?
-			delay(2000);
-			esp_restart();
+			// Only call submitFunc when it has been set to something useful
+			if( submitFunc ) submitFunc();
 	});
 
 	server.onNotFound([this](AsyncWebServerRequest *request)
@@ -208,3 +207,16 @@ void WebServer::setInterfaceElementAttribute(const String &id, const String &key
 		}
 	}
 }
+
+void WebServer::reset() {
+	interfaceElements.clear();
+	// We should also reset the server itself, according to documentation, but it will cause a crash.
+	// It works without reset, if you only configure one server after a reboot. Not sure what happens if you want to reconfigure during runtime.
+	//server.reset();
+	//server.addHandler(&events);
+//#ifdef BASECAMP_USEDNS
+//#ifdef DNSServer_h
+	//server.addHandler(new CaptiveRequestHandler()).setFilter(ON_AP_FILTER);
+//#endif
+//#endif
+}

WebServer.hpp

@@ -30,12 +30,18 @@ class WebServer {
 		WebServer();
 		~WebServer() = default;
 
-		void begin(Configuration &configuration);
+		void begin(Configuration &configuration, std::function<void()> submitFunc = 0);
 		bool addURL(const char* url, const char* content, const char* mimetype);
+
+		// Remark: The server should be stopped before any changes to the interface elements are done to avoid inconsistent results if a request comes in at that very moment.
+		// However, ESPAsyncWebServer does not support any kind of end() function or something like that in the moment.
 		void addInterfaceElement(const String &id, String element, String content, String parent = "#configform", String configvariable = "");
 
 		// Sets "key" to "value" in element with id "id" if exists.
 		void setInterfaceElementAttribute(const String &id, const String &key, String value);
+
+		// Removes all interface elements
+		void reset();
 
 		struct cmp_str
 		{