feat: switch from casbin to pycasbin

diff --git a/requirements.txt b/requirements.txt
index ff494e6..7f55f36 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,2 @@
 django

-casbin
\ No newline at end of file
+pycasbin>=2.0.0
\ No newline at end of file