island: Replace private static functions in Authenticator with functions

In python, private static methods serve no purpose. Python has
first-class functions; let's use them.

monkey/monkey_island/cc/resources/auth/auth.py

@@ -38,15 +38,15 @@ class Authenticate(flask_restful.Resource):
             "password": "my_password"
         }
         """
-        (username, password) = Authenticate._get_credentials_from_request(request)
+        (username, password) = _get_credentials_from_request(request)
 
-        if self._credentials_match_registered_user(username, password):
-            access_token = Authenticate._create_access_token(username)
+        if _credentials_match_registered_user(username, password):
+            access_token = _create_access_token(username)
             return make_response({"access_token": access_token, "error": ""}, 200)
         else:
             return make_response({"error": "Invalid credentials"}, 401)
 
-    @staticmethod
+
 def _get_credentials_from_request(request):
     credentials = json.loads(request.data)
 
@@ -55,7 +55,7 @@ class Authenticate(flask_restful.Resource):
 
     return (username, password)
 
-    @staticmethod
+
 def _credentials_match_registered_user(username, password):
     user = user_store.UserStore.username_table.get(username, None)
     if user and bcrypt.checkpw(password.encode("utf-8"), user.secret.encode("utf-8")):
@@ -63,14 +63,12 @@ class Authenticate(flask_restful.Resource):
 
     return False
 
-    @staticmethod
+
 def _create_access_token(username):
     access_token = flask_jwt_extended.create_access_token(
         identity=user_store.UserStore.username_table[username].id
     )
-        logger.debug(
-            f"Created access token for user {username} that begins with {access_token[:4]}"
-        )
+    logger.debug(f"Created access token for user {username} that begins with {access_token[:4]}")
 
     return access_token