v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/model/incoming_webhook_test.go

@@ -0,0 +1,152 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIncomingWebhookIsValid(t *testing.T) {
+	o := IncomingWebhook{}
+
+	require.NotNil(t, o.IsValid())
+
+	o.Id = NewId()
+	require.NotNil(t, o.IsValid())
+
+	o.CreateAt = GetMillis()
+	require.NotNil(t, o.IsValid())
+
+	o.UpdateAt = GetMillis()
+	require.NotNil(t, o.IsValid())
+
+	o.UserId = "123"
+	require.NotNil(t, o.IsValid())
+
+	o.UserId = NewId()
+	require.NotNil(t, o.IsValid())
+
+	o.ChannelId = "123"
+	require.NotNil(t, o.IsValid())
+
+	o.ChannelId = NewId()
+	require.NotNil(t, o.IsValid())
+
+	o.TeamId = "123"
+	require.NotNil(t, o.IsValid())
+
+	o.TeamId = NewId()
+	require.Nil(t, o.IsValid())
+
+	o.DisplayName = strings.Repeat("1", 65)
+	require.NotNil(t, o.IsValid())
+
+	o.DisplayName = strings.Repeat("1", 64)
+	require.Nil(t, o.IsValid())
+
+	o.Description = strings.Repeat("1", 501)
+	require.NotNil(t, o.IsValid())
+
+	o.Description = strings.Repeat("1", 500)
+	require.Nil(t, o.IsValid())
+
+	o.Username = strings.Repeat("1", 65)
+	require.NotNil(t, o.IsValid())
+
+	o.Username = strings.Repeat("1", 64)
+	require.Nil(t, o.IsValid())
+
+	o.IconURL = strings.Repeat("1", 1025)
+	require.NotNil(t, o.IsValid())
+
+	o.IconURL = strings.Repeat("1", 1024)
+	require.Nil(t, o.IsValid())
+}
+
+func TestIncomingWebhookPreSave(t *testing.T) {
+	o := IncomingWebhook{}
+	o.PreSave()
+}
+
+func TestIncomingWebhookPreUpdate(t *testing.T) {
+	o := IncomingWebhook{}
+	o.PreUpdate()
+}
+
+func TestIncomingWebhookRequestFromJSON(t *testing.T) {
+	texts := []string{
+		`this is a test`,
+		`this is a test
+			that contains a newline and tabs`,
+		`this is a test \"foo
+			that contains a newline and tabs`,
+		`this is a test \"foo\"
+			that contains a newline and tabs`,
+		`this is a test \"foo\"
+		\"			that contains a newline and tabs`,
+		`this is a test \"foo\"
+
+		\"			that contains a newline and tabs
+		`,
+	}
+
+	for _, text := range texts {
+		// build a sample payload with the text
+		payload := `{
+        "text": "` + text + `",
+        "attachments": [
+            {
+                "fallback": "` + text + `",
+
+                "color": "#36a64f",
+
+                "pretext": "` + text + `",
+
+                "author_name": "` + text + `",
+                "author_link": "http://flickr.com/bobby/",
+                "author_icon": "http://flickr.com/icons/bobby.jpg",
+
+                "title": "` + text + `",
+                "title_link": "https://api.slack.com/",
+
+                "text": "` + text + `",
+
+                "fields": [
+                    {
+                        "title": "` + text + `",
+                        "value": "` + text + `",
+                        "short": false
+                    }
+                ],
+
+                "image_url": "http://my-website.com/path/to/image.jpg",
+                "thumb_url": "http://example.com/path/to/thumb.png"
+            }
+        ]
+    }`
+
+		// try to create an IncomingWebhookRequest from the payload
+		data := strings.NewReader(payload)
+		iwr, _ := IncomingWebhookRequestFromJSON(data)
+
+		// After it has been decoded, the JSON string won't contain the escape char anymore
+		expected := strings.Replace(text, `\"`, `"`, -1)
+		require.NotNil(t, iwr)
+		require.Equal(t, expected, iwr.Text)
+
+		attachment := iwr.Attachments[0]
+		require.Equal(t, expected, attachment.Text)
+	}
+}
+
+func TestIncomingWebhookNullArrayItems(t *testing.T) {
+	payload := `{"attachments":[{"fields":[{"title":"foo","value":"bar","short":true}, null]}, null]}`
+	iwr, _ := IncomingWebhookRequestFromJSON(strings.NewReader(payload))
+	require.NotNil(t, iwr)
+	require.Len(t, iwr.Attachments, 1)
+	require.Len(t, iwr.Attachments[0].Fields, 1)
+}