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/draft_test.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDraftIsValid(t *testing.T) {
+	o := Draft{}
+	maxDraftSize := 10000
+
+	err := o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.CreateAt = GetMillis()
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.UpdateAt = GetMillis()
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.UserId = NewId()
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.ChannelId = NewId()
+	o.RootId = "123"
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.RootId = ""
+
+	o.Message = strings.Repeat("0", maxDraftSize+1)
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+
+	o.Message = strings.Repeat("0", maxDraftSize)
+	err = o.IsValid(maxDraftSize)
+	assert.Nil(t, err)
+
+	o.Message = "test"
+	err = o.IsValid(maxDraftSize)
+	assert.Nil(t, err)
+
+	o.FileIds = StringArray{strings.Repeat("0", maxDraftSize+1)}
+	err = o.IsValid(maxDraftSize)
+	assert.NotNil(t, err)
+}
+
+func TestDraftPreSave(t *testing.T) {
+	o := Draft{Message: "test"}
+	o.PreSave()
+
+	assert.NotEqual(t, 0, o.CreateAt)
+
+	past := GetMillis() - 1
+	o = Draft{Message: "test", CreateAt: past}
+	o.PreSave()
+
+	assert.LessOrEqual(t, o.CreateAt, past)
+}