[Feature] support return err in GetPermissionsForUser

[dacongda]

Want to prioritize this issue? Try:

---

Is your feature request related to a problem? Please describe.

func main() {
	e, err := casbin.NewEnforcer("example/policy.conf", "example/policy.csv")

	if err != nil {
		log.Fatalf("err :adapter: %s", err)
	}

	// e.SetFieldIndex("p", "app", 2)
	e.SetFieldIndex("p", "dom", 1)

	res := e.GetPermissionsForUser("invoice", "app")

	println(len(res))
}

[request_definition]
r = RoleId, domain, TypeQuery, operationName

[policy_definition]
p = RoleId, domain, TypeQuery, operationName, eft, scope

[role_definition]
g = _, _, _

[policy_effect]
e = some(where (p.eft == allow)) && !some(where (p.eft == deny))

[matchers]
m = g(r.RoleId, p.RoleId, r.domain) && r.domain == p.domain && r.TypeQuery == p.TypeQuery && r.operationName == p.operationName

When I use above code and model conf , if have't e.SetFieldIndex("p", "dom", 1) ,the programme will not report any error , and just return an empty result , by the way, it seems that func GetNamedPermissionsForUser only use the first elment of domain list.

Describe the solution you'd like
Throw an error like "dom index is not set, please use enforcer.SetFieldIndex() to set index" or support use dynamic domainIndex

Describe alternatives you've considered
Create a new func that support return err msg or just rewrite this func

Additional context

[casbin-bot]

@tangyang9464 @JalinWang

[hsluoyz]

@dacongda can you make a PR?

[ankan20]

Is it assigned to anyone or is it closed?