Make content type mandatory since BBB 2.7.8

# Conflicts:
#	src/BigBlueButton.php

Author: GhaziTriki

src/BigBlueButton.php

@@ -558,18 +558,24 @@ private function sendRequest(string $url, string $payload = '', string $contentT
             }
         }
 
+        // Initialise headers array with mandatory Content-type
+        $headers = [
+            'Content-type: ' . $contentType,
+        ];
+
         // PAYLOAD
         if (!empty($payload)) {
             curl_setopt($ch, CURLOPT_HEADER, 0);
             curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
             curl_setopt($ch, CURLOPT_POST, 1);
             curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
-            curl_setopt($ch, CURLOPT_HTTPHEADER, [
-                'Content-type: ' . $contentType,
-                'Content-length: ' . strlen($payload),
-            ]);
+            // Add Content-length header if payload is present
+            $headers[] = 'Content-length: ' . strlen($payload);
         }
 
+        // Set HTTP headers
+        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
+
         // OTHERS
         foreach ($this->curlOpts as $opt => $value) {
             curl_setopt($ch, $opt, $value);