[Feature] Implement subjectPriority in jcasbin

[coffeeZhang001]

I am usring casbin with jcasbin library, but i found the [load-policy-with-priority-based-on-role-and-user-hierarchy] feature is not implementd in jcasbin.

I think this feature is valuable and convenient when we want to define policy with priority.

Currently, i have to define priority for each policy like this:

p, 10, data1_deny_group, data1, read, deny
p, 10, data1_deny_group, data1, write, deny

[casbin-bot]

@tangyang9464 @JalinWang

[hsluoyz]

@imp2002

/cc @tangyang9464

[casbin-bot]

@tangyang9464 @imp2002

[TraMiu]

Yes, I think this feature is important too.

[imp2002]

I will try sync this feature.

[Xhy-5000]

what's the usage of this mthod?https://github.com/casbin/casbin/blob/4028f8a8f4cf3ee76056da41bbd596ec97baac2a/model/model.go#L242

[Xhy-5000]

@imp2002 Do you know that?