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/guest_invite.go

@@ -0,0 +1,46 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"net/http"
+)
+
+type GuestsInvite struct {
+	Emails   []string `json:"emails"`
+	Channels []string `json:"channels"`
+	Message  string   `json:"message"`
+}
+
+func (i *GuestsInvite) Auditable() map[string]interface{} {
+	return map[string]interface{}{
+		"emails":   i.Emails,
+		"channels": i.Channels,
+	}
+}
+
+// IsValid validates the user and returns an error if it isn't configured
+// correctly.
+func (i *GuestsInvite) IsValid() *AppError {
+	if len(i.Emails) == 0 {
+		return NewAppError("GuestsInvite.IsValid", "model.guest.is_valid.emails.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	for _, email := range i.Emails {
+		if len(email) > UserEmailMaxLength || email == "" || !IsValidEmail(email) {
+			return NewAppError("GuestsInvite.IsValid", "model.guest.is_valid.email.app_error", nil, "email="+email, http.StatusBadRequest)
+		}
+	}
+
+	if len(i.Channels) == 0 {
+		return NewAppError("GuestsInvite.IsValid", "model.guest.is_valid.channels.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	for _, channel := range i.Channels {
+		if len(channel) != 26 {
+			return NewAppError("GuestsInvite.IsValid", "model.guest.is_valid.channel.app_error", nil, "channel="+channel, http.StatusBadRequest)
+		}
+	}
+	return nil
+}