consider support async matcher function

[wasdee]

Action

I want author to provide some directions about interface design if he agreed. so I or others can have confident in creating PR.

Rationale

AsyncManagementEnforcer.add_function accept only sync funciton. there will throw an error. when AsyncManagementEnforcer.enforce get called.

python stack embraces a lot of async this is an inconvenient to implentment sync match function only for using it with casbin

The Error

        explain_index = -1
        if not 0 == policy_len:
            for i, pvals in enumerate(self.model["p"][ptype].policy):
                if len(p_tokens) != len(pvals):
                    raise RuntimeError("invalid policy size")
                p_parameters = dict(zip(p_tokens, pvals))
                parameters = dict(r_parameters, **p_parameters)
                if exp_has_eval:
                    rule_names = util.get_eval_value(exp_string)
                    rules = [util.escape_assertion(p_parameters[rule_name]) for rule_name in rule_names]
                    exp_with_rule = util.replace_eval(exp_string, rules)
                    expression = self._get_expression(exp_with_rule, functions)
                result = expression.eval(parameters)
                if isinstance(result, bool):
                    if not result:
                        policy_effects.add(Effector.INDETERMINATE)
                        continue
                elif isinstance(result, float):
                    if 0 == result:
                        policy_effects.add(Effector.INDETERMINATE)
                        continue
                else:
>                   raise RuntimeError("matcher result should be bool, int or float")
E                   RuntimeError: matcher result should be bool, int or float
 
.venv/lib/python3.11/site-packages/casbin/core_enforcer.py:469: RuntimeError
=================================================================================== short test summary info ====================================================================================
FAILED tests/test_casbin/test_plan_enforcement.py::test_plan_enforcement - RuntimeError: matcher result should be bool, int or float

Suggestion

0. add_function could support both sync and async dynamically
1. create await enforce.enforce() async function
   1. might need a separate class or new function name ``
2. use async.gather() for perf await enforce.batch_enforce()