add encryption (#1002)

* add encryption

* add doc

* add doc

* fix bug

tests/models/test_encryption.py

@@ -0,0 +1,9 @@
+import fastdeploy as fd
+import os
+
+if __name__ == "__main__":
+    input = "Hello"
+    cipher, key = fd.encryption.encrypt(input)
+    output = fd.encryption.decrypt(cipher, key)
+    assert input == output, "test encryption failed"
+    print("test encryption success")