Add sendContent overload that takes a const char* and a length (#4276)

The web server currently lacks the ability to send a buffer. Only strings are supported.

This PR adds an overload to sendContent.

libraries/WebServer/src/WebServer.cpp

@@ -463,20 +463,23 @@ void WebServer::send(int code, const String& content_type, const String& content
 }
 
 void WebServer::sendContent(const String& content) {
+  sendContent(content.c_str(), content.length());
+}
+
+void WebServer::sendContent(const char* content, size_t contentLength) {
   const char * footer = "\r\n";
-  size_t len = content.length();
   if(_chunked) {
     char * chunkSize = (char *)malloc(11);
     if(chunkSize){
-      sprintf(chunkSize, "%x%s", len, footer);
+      sprintf(chunkSize, "%x%s", contentLength, footer);
       _currentClientWrite(chunkSize, strlen(chunkSize));
       free(chunkSize);
     }
   }
-  _currentClientWrite(content.c_str(), len);
+  _currentClientWrite(content, contentLength);
   if(_chunked){
     _currentClient.write(footer, 2);
-    if (len == 0) {
+    if (contentLength == 0) {
       _chunked = false;
     }
   }

libraries/WebServer/src/WebServer.h

@@ -130,6 +130,7 @@ public:
   void setContentLength(const size_t contentLength);
   void sendHeader(const String& name, const String& value, bool first = false);
   void sendContent(const String& content);
+  void sendContent(const char* content, size_t contentLength);
   void sendContent_P(PGM_P content);
   void sendContent_P(PGM_P content, size_t size);