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/modeltestlib_test.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func CheckInt(t *testing.T, got int, expected int) {
+	assert.Equal(t, got, expected)
+}
+
+func CheckString(t *testing.T, got string, expected string) {
+	assert.Equal(t, got, expected)
+}
+
+func CheckTrue(t *testing.T, test bool) {
+	assert.True(t, test)
+}
+
+func CheckFalse(t *testing.T, test bool) {
+	assert.False(t, test)
+}