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/plugin/product.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package plugin
+
+import (
+	"net/http"
+)
+
+type RegisteredProduct struct {
+	ProductID string
+	Adapter   Hooks
+}
+
+func (rp *RegisteredProduct) Implements(hookId int) bool {
+	adapter, ok := rp.Adapter.(*HooksAdapter)
+	if !ok {
+		return false
+	}
+
+	_, ok = adapter.implemented[hookId]
+	return ok
+}
+
+// Implemented method is overridden intentionally to prevent calling it from outside.
+func (a *HooksAdapter) Implemented() ([]string, error) {
+	return nil, nil
+}
+
+// OnActivate is overridden intentionally as product should not call it.
+func (a *HooksAdapter) OnActivate() error {
+	return nil
+}
+
+// OnDeactivate is overridden intentionally as product should not call it.
+func (a *HooksAdapter) OnDeactivate() error {
+	return nil
+}
+
+// ServeHTTP is overridden intentionally as product should not call it.
+func (a *HooksAdapter) ServeHTTP(c *Context, w http.ResponseWriter, r *http.Request) {}