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/cluster_discovery_test.go

@@ -0,0 +1,50 @@
+// 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 TestClusterDiscovery(t *testing.T) {
+	o := ClusterDiscovery{
+		Type:        "test_type",
+		ClusterName: "cluster_name",
+		Hostname:    "test_hostname",
+	}
+
+	result1 := o
+	result2 := o
+	result3 := o
+
+	o.Id = "0"
+	result1.Id = "1"
+	result2.Id = "2"
+	result3.Id = "3"
+	result3.Hostname = "something_diff"
+
+	assert.True(t, o.IsEqual(&result1))
+
+	list := make([]*ClusterDiscovery, 0)
+	list = append(list, &o)
+	list = append(list, &result1)
+	list = append(list, &result2)
+	list = append(list, &result3)
+
+	rlist := FilterClusterDiscovery(list, func(in *ClusterDiscovery) bool {
+		return !o.IsEqual(in)
+	})
+
+	assert.Len(t, rlist, 1)
+
+	o.AutoFillHostname()
+	o.Hostname = ""
+	o.AutoFillHostname()
+
+	o.AutoFillIPAddress("", "")
+	o.Hostname = ""
+	o.AutoFillIPAddress("", "")
+}