Explain enforcement in log

[dovics]

For #355
Explain why an enforcement was or wasn't satisfied.Controlled by autoExplain in enforce,Print the policy related to the result to the log.

such as some(where (p.eft == allow)), the explanation will be all allowed policy.

whether it hits depends on user selected effect. User can modify it by interface EffectorEx

[coveralls]

Coverage increased (+1.5%) to 73.322% when pulling 5585d2a on dovics:explian into 907df79 on casbin:master.

[hsluoyz]

I think logs are not very friendly for users. They want to return matched rules:

In some scenarios it would be useful to have a way to explain why an enforcement was or wasn't satisfied.
The simplest idea could be to just inform of the matched rules that allowed satisfying (or not) the model.

Can we add a function called EnforceEx(), which is similar to Enforce(), but returns matched rule(s) additionally?

[dovics]

what do you think of changing the signature of enforce()

func (e *Enforcer) enforce(matcher string, rvals ...interface{}) (ok bool,explains [][]string,  err error)

or

func (e *Enforcer) enforce(matcher string, explains *[][]string, rvals ...interface{}) (ok bool, err error)

otherwise we need to split enforce(), I think it is difficult to do

[dovics]

@hsluoyz,@nodece, I try to add EnforceEx() and EnforceExWithMatch().

I think it is better to return all the policies related to the result. And the result and hitPolicies are returned directly in the return value

[nodece]

Thanks @dovics , Must approve.

[hsluoyz]

[nodece]

@hsluoyz Is there any progress?

[hsluoyz]

lgtm

[github-actions]

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