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/user_access_token_test.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUserAccessTokenIsValid(t *testing.T) {
+	ad := UserAccessToken{}
+
+	appErr := ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.id.app_error")
+
+	ad.Id = NewRandomString(26)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.token.app_error")
+
+	ad.Token = NewRandomString(26)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.user_id.app_error")
+
+	ad.UserId = NewRandomString(26)
+	require.Nil(t, ad.IsValid())
+
+	ad.Description = NewRandomString(256)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.description.app_error")
+}