add isAdmin to user model (#6231)

update vendor and add tests

fix swagger

routers/api/v1/user/user.go

@@ -75,6 +75,7 @@ func Search(ctx *context.APIContext) {
 			UserName:  users[i].Name,
 			AvatarURL: users[i].AvatarLink(),
 			FullName:  markup.Sanitize(users[i].FullName),
+			IsAdmin:   users[i].IsAdmin,
 		}
 		if ctx.IsSigned && (!users[i].KeepEmailPrivate || ctx.User.IsAdmin) {
 			results[i].Email = users[i].Email