AllowEditPost and PostEditTimeLimit migration (#8208)

* AllowEditPost and PostEditTimeLimit migration

* Not set EDIT_POST permission to sysadmin_role if ALLOW_EDIT_POST is configured to NEVER

* Remove a bit of code duplication

app/post.go

@@ -332,13 +332,6 @@ func (a *App) UpdatePost(post *model.Post, safeUpdate bool) (*model.Post, *model
 	} else {
 		oldPost = result.Data.(*model.PostList).Posts[post.Id]
 
-		if a.License() != nil {
-			if *a.Config().ServiceSettings.AllowEditPost == model.ALLOW_EDIT_POST_NEVER && post.Message != oldPost.Message {
-				err := model.NewAppError("UpdatePost", "api.post.update_post.permissions_denied.app_error", nil, "", http.StatusForbidden)
-				return nil, err
-			}
-		}
-
 		if oldPost == nil {
 			err := model.NewAppError("UpdatePost", "api.post.update_post.find.app_error", nil, "id="+post.Id, http.StatusBadRequest)
 			return nil, err
@@ -355,7 +348,7 @@ func (a *App) UpdatePost(post *model.Post, safeUpdate bool) (*model.Post, *model
 		}
 
 		if a.License() != nil {
-			if *a.Config().ServiceSettings.AllowEditPost == model.ALLOW_EDIT_POST_TIME_LIMIT && model.GetMillis() > oldPost.CreateAt+int64(*a.Config().ServiceSettings.PostEditTimeLimit*1000) && post.Message != oldPost.Message {
+			if *a.Config().ServiceSettings.PostEditTimeLimit != -1 && model.GetMillis() > oldPost.CreateAt+int64(*a.Config().ServiceSettings.PostEditTimeLimit*1000) && post.Message != oldPost.Message {
 				err := model.NewAppError("UpdatePost", "api.post.update_post.permissions_time_limit.app_error", map[string]interface{}{"timeLimit": *a.Config().ServiceSettings.PostEditTimeLimit}, "", http.StatusBadRequest)
 				return nil, err
 			}