make frame fromBinary public, improve docs

src/Http2Middleware.php

@@ -22,17 +22,33 @@ class Http2Middleware
 
     public function __invoke(ServerRequestInterface $request, ?callable $next=null)
     {
+        // expect upgrade h2 for secure connections, h2c for plaintext
+
+        // TODO handle HTTP/2 upgrade from HTTP/1.1
+        // TODO handle HTTP/2 with prior knowledge
 
     }
 
+    /**
+     * Parse the settings frame present in the HTTP/1.1 upgrade request.
+     * 
+     * @param string $settings
+     * @return SettingsFrame
+     */
     private function parseSettingsFromBase64String(string $settings): SettingsFrame
     {
         $decoded = base64_decode($settings);
         $frame = new SettingsFrame();
-        $frame->parseFrame($decoded);
+        $frame->fromBinary($decoded);
         return $frame;
     }
 
+    /**
+     * Prepare a connection for the HTTP/2 session.
+     * 
+     * @param ServerRequestInterface $request
+     * @return Http2Connection
+     */
     private function setupConnection(ServerRequestInterface $request): Http2Connection
     {
         $stream = new ThroughStream();