[API] generalize list header (#16551)

* Add info about list endpoints to CONTRIBUTING.md

* Let all list endpoints return X-Total-Count header 

* Add TODOs for GetCombinedCommitStatusByRef

* Fix models/issue_stopwatch.go

* Rrefactor models.ListDeployKeys

* Introduce helper func and use them for SetLinkHeader related func

modules/context/org.go

@@ -123,8 +123,8 @@ func HandleOrgAssignment(ctx *Context, args ...bool) {
 	// Team.
 	if ctx.Org.IsMember {
 		if ctx.Org.IsOwner {
-			if err := org.GetTeams(&models.SearchTeamOptions{}); err != nil {
-				ctx.ServerError("GetTeams", err)
+			if err := org.LoadTeams(); err != nil {
+				ctx.ServerError("LoadTeams", err)
 				return
 			}
 		} else {