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/command_webhook_test.go

@@ -0,0 +1,60 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCommandWebhookPreSave(t *testing.T) {
+	h := CommandWebhook{}
+	h.PreSave()
+
+	require.Len(t, h.Id, 26, "Id should be generated")
+	require.NotEqual(t, 0, h.CreateAt, "CreateAt should be set")
+}
+
+func TestCommandWebhookIsValid(t *testing.T) {
+	h := CommandWebhook{}
+	h.Id = NewId()
+	h.CreateAt = GetMillis()
+	h.CommandId = NewId()
+	h.UserId = NewId()
+	h.ChannelId = NewId()
+
+	for _, test := range []struct {
+		Transform     func()
+		ExpectedError string
+	}{
+		{func() {}, ""},
+		{func() { h.Id = "asd" }, "model.command_hook.id.app_error"},
+		{func() { h.Id = NewId() }, ""},
+		{func() { h.CreateAt = 0 }, "model.command_hook.create_at.app_error"},
+		{func() { h.CreateAt = GetMillis() }, ""},
+		{func() { h.CommandId = "asd" }, "model.command_hook.command_id.app_error"},
+		{func() { h.CommandId = NewId() }, ""},
+		{func() { h.UserId = "asd" }, "model.command_hook.user_id.app_error"},
+		{func() { h.UserId = NewId() }, ""},
+		{func() { h.ChannelId = "asd" }, "model.command_hook.channel_id.app_error"},
+		{func() { h.ChannelId = NewId() }, ""},
+		{func() { h.RootId = "asd" }, "model.command_hook.root_id.app_error"},
+		{func() { h.RootId = NewId() }, ""},
+	} {
+		tmp := h
+		test.Transform()
+		appErr := h.IsValid()
+
+		if test.ExpectedError == "" {
+			assert.Nil(t, appErr, "hook should be valid")
+		} else {
+			require.NotNil(t, appErr)
+			assert.Equal(t, test.ExpectedError, appErr.Id, "expected "+test.ExpectedError+" error")
+		}
+
+		h = tmp
+	}
+}