Move permissions code into app package (#5146)

* Move permissions code into app package

* Revert getPosts permission

api/deprecated.go

@@ -32,7 +32,8 @@ func InitDeprecated() {
 func getMoreChannels(c *Context, w http.ResponseWriter, r *http.Request) {
 
 	// user is already in the team
-	if !HasPermissionToTeamContext(c, c.TeamId, model.PERMISSION_LIST_TEAM_CHANNELS) {
+	if !app.SessionHasPermissionToTeam(c.Session, c.TeamId, model.PERMISSION_LIST_TEAM_CHANNELS) {
+		c.SetPermissionError(model.PERMISSION_LIST_TEAM_CHANNELS)
 		return
 	}