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/post_acknowledgement.go

@@ -0,0 +1,24 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import "net/http"
+
+type PostAcknowledgement struct {
+	UserId         string `json:"user_id"`
+	PostId         string `json:"post_id"`
+	AcknowledgedAt int64  `json:"acknowledged_at"`
+}
+
+func (o *PostAcknowledgement) IsValid() *AppError {
+	if !IsValidId(o.UserId) {
+		return NewAppError("PostAcknowledgement.IsValid", "model.acknowledgement.is_valid.user_id.app_error", nil, "user_id="+o.UserId, http.StatusBadRequest)
+	}
+
+	if !IsValidId(o.PostId) {
+		return NewAppError("PostAcknowledgement.IsValid", "model.acknowledgement.is_valid.post_id.app_error", nil, "post_id="+o.PostId, http.StatusBadRequest)
+	}
+
+	return nil
+}