PLT-1649: add response_url support for custom slash commands (#6739)

* add response_url support for custom slash commands

* pr suggestions

* pr update / suggestion

* test fix

store/sql_command_webhook_store_test.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package store
+
+import (
+	"testing"
+
+	"net/http"
+
+	"github.com/mattermost/platform/model"
+)
+
+func TestCommandWebhookStore(t *testing.T) {
+	Setup()
+
+	cws := store.CommandWebhook()
+
+	h1 := &model.CommandWebhook{}
+	h1.CommandId = model.NewId()
+	h1.UserId = model.NewId()
+	h1.ChannelId = model.NewId()
+	h1 = (<-cws.Save(h1)).Data.(*model.CommandWebhook)
+
+	if r1 := <-cws.Get(h1.Id); r1.Err != nil {
+		t.Fatal(r1.Err)
+	} else {
+		if *r1.Data.(*model.CommandWebhook) != *h1 {
+			t.Fatal("invalid returned webhook")
+		}
+	}
+
+	if err := (<-cws.Get("123")).Err; err.StatusCode != http.StatusNotFound {
+		t.Fatal("Should have set the status as not found for missing id")
+	}
+
+	h2 := &model.CommandWebhook{}
+	h2.CreateAt = model.GetMillis() - 2*model.COMMAND_WEBHOOK_LIFETIME
+	h2.CommandId = model.NewId()
+	h2.UserId = model.NewId()
+	h2.ChannelId = model.NewId()
+	h2 = (<-cws.Save(h2)).Data.(*model.CommandWebhook)
+
+	if err := (<-cws.Get(h2.Id)).Err; err == nil || err.StatusCode != http.StatusNotFound {
+		t.Fatal("Should have set the status as not found for expired webhook")
+	}
+
+	cws.Cleanup()
+
+	if err := (<-cws.Get(h1.Id)).Err; err != nil {
+		t.Fatal("Should have no error getting unexpired webhook")
+	}
+
+	if err := (<-cws.Get(h2.Id)).Err; err.StatusCode != http.StatusNotFound {
+		t.Fatal("Should have set the status as not found for expired webhook")
+	}
+
+	if err := (<-cws.TryUse(h1.Id, 1)).Err; err != nil {
+		t.Fatal("Should be able to use webhook once")
+	}
+
+	if err := (<-cws.TryUse(h1.Id, 1)).Err; err == nil || err.StatusCode != http.StatusBadRequest {
+		t.Fatal("Should be able to use webhook once")
+	}
+}