Add requires_authorization utility

tests/test_app.py

@@ -1,7 +1,7 @@
 import os
 
 from flask import Flask, redirect, url_for
-from flask_discord import DiscordOAuth2Session
+from flask_discord import DiscordOAuth2Session, requires_authorization
 
 
 app = Flask(__name__)
@@ -79,5 +79,11 @@ def logout():
     return redirect(url_for(".index"))
 
 
+@app.route("/secret/")
+@requires_authorization
+def secret():
+    return os.urandom(16)
+
+
 if __name__ == "__main__":
     app.run(debug=True)