Пример вызова Rest Service

this.dbQueryService.restapiPost("wa_chat_send",{msg : this.f.text.value , chat_id : this.currentChat.id})
                        .pipe(first())
                        .subscribe(items => {
                                this.f.text.setValue('');
                                setTimeout(() => document.getElementById("bottom").scrollIntoView(), 100);
                        });