feat(auth): implement user authentication system

backend/node_modules/is-stream/index.js

@@ -0,0 +1,28 @@
+'use strict';
+
+const isStream = stream =>
+	stream !== null &&
+	typeof stream === 'object' &&
+	typeof stream.pipe === 'function';
+
+isStream.writable = stream =>
+	isStream(stream) &&
+	stream.writable !== false &&
+	typeof stream._write === 'function' &&
+	typeof stream._writableState === 'object';
+
+isStream.readable = stream =>
+	isStream(stream) &&
+	stream.readable !== false &&
+	typeof stream._read === 'function' &&
+	typeof stream._readableState === 'object';
+
+isStream.duplex = stream =>
+	isStream.writable(stream) &&
+	isStream.readable(stream);
+
+isStream.transform = stream =>
+	isStream.duplex(stream) &&
+	typeof stream._transform === 'function';
+
+module.exports = isStream;