Restrict permission check on repositories and fix some problems (#5314)

* fix units permission problems

* fix some bugs and merge LoadUnits to repoAssignment

* refactor permission struct and add some copyright heads

* remove unused codes

* fix routes units check

* improve permission check

* add unit tests for permission

* fix typo

* fix tests

* fix some routes

* fix api permission check

* improve permission check

* fix some permission check

* fix tests

* fix tests

* improve some permission check

* fix some permission check

* refactor AccessLevel

* fix bug

* fix tests

* fix tests

* fix tests

* fix AccessLevel

* rename CanAccess

* fix tests

* fix comment

* fix bug

* add missing unit for test repos

* fix bug

* rename some functions

* fix routes check

routers/api/v1/repo/fork.go

@@ -7,7 +7,6 @@ package repo
 import (
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/context"
-	"code.gitea.io/gitea/routers/api/v1/utils"
 
 	api "code.gitea.io/sdk/gitea"
 )
@@ -40,7 +39,7 @@ func ListForks(ctx *context.APIContext) {
 	}
 	apiForks := make([]*api.Repository, len(forks))
 	for i, fork := range forks {
-		access, err := models.AccessLevel(utils.UserID(ctx), fork)
+		access, err := models.AccessLevel(ctx.User, fork)
 		if err != nil {
 			ctx.Error(500, "AccessLevel", err)
 			return