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_response.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"encoding/json"
+	"io"
+	"strings"
+
+	"github.com/mattermost/mattermost-server/server/v8/channels/utils/jsonutils"
+)
+
+const (
+	CommandResponseTypeInChannel = "in_channel"
+	CommandResponseTypeEphemeral = "ephemeral"
+)
+
+type CommandResponse struct {
+	ResponseType     string             `json:"response_type"`
+	Text             string             `json:"text"`
+	Username         string             `json:"username"`
+	ChannelId        string             `json:"channel_id"`
+	IconURL          string             `json:"icon_url"`
+	Type             string             `json:"type"`
+	Props            StringInterface    `json:"props"`
+	GotoLocation     string             `json:"goto_location"`
+	TriggerId        string             `json:"trigger_id"`
+	SkipSlackParsing bool               `json:"skip_slack_parsing"` // Set to `true` to skip the Slack-compatibility handling of Text.
+	Attachments      []*SlackAttachment `json:"attachments"`
+	ExtraResponses   []*CommandResponse `json:"extra_responses"`
+}
+
+func CommandResponseFromHTTPBody(contentType string, body io.Reader) (*CommandResponse, error) {
+	if strings.TrimSpace(strings.Split(contentType, ";")[0]) == "application/json" {
+		return CommandResponseFromJSON(body)
+	}
+	if b, err := io.ReadAll(body); err == nil {
+		return CommandResponseFromPlainText(string(b)), nil
+	}
+	return nil, nil
+}
+
+func CommandResponseFromPlainText(text string) *CommandResponse {
+	return &CommandResponse{
+		Text: text,
+	}
+}
+
+func CommandResponseFromJSON(data io.Reader) (*CommandResponse, error) {
+	b, err := io.ReadAll(data)
+	if err != nil {
+		return nil, err
+	}
+
+	var o CommandResponse
+	err = json.Unmarshal(b, &o)
+	if err != nil {
+		return nil, jsonutils.HumanizeJSONError(err, b)
+	}
+
+	o.Attachments = StringifySlackFieldValue(o.Attachments)
+
+	if o.ExtraResponses != nil {
+		for _, resp := range o.ExtraResponses {
+			resp.Attachments = StringifySlackFieldValue(resp.Attachments)
+		}
+	}
+
+	return &o, nil
+}