Expose public/ API as submodule (#23345)

* model -> public/model

* plugin -> public/plugin

* public/model/utils -> public/utils

* platform/shared/mlog -> public/shared/mlog

* platform/shared/i18n -> public/shared/i18n

* platform/shared/markdown -> public/shared/markdown

* platform/services/timezones -> public/shared/timezones

* channels/einterfaces -> einterfaces

* expose public/ submodule

* go mod tidy

* .github: cache-dependency-path, setup-go-work

* modules-tidy for public/ too

* remove old gomodtidy

server/public/model/channel_count.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"crypto/md5"
+	"fmt"
+	"sort"
+	"strconv"
+)
+
+type ChannelCounts struct {
+	Counts      map[string]int64 `json:"counts"`
+	CountsRoot  map[string]int64 `json:"counts_root"`
+	UpdateTimes map[string]int64 `json:"update_times"`
+}
+
+func (o *ChannelCounts) Etag() string {
+	// we don't include CountsRoot in ETag calculation, since it's a derivative
+	ids := []string{}
+	for id := range o.Counts {
+		ids = append(ids, id)
+	}
+	sort.Strings(ids)
+
+	str := ""
+	for _, id := range ids {
+		str += id + strconv.FormatInt(o.Counts[id], 10)
+	}
+
+	md5Counts := fmt.Sprintf("%x", md5.Sum([]byte(str)))
+
+	var update int64 = 0
+	for _, u := range o.UpdateTimes {
+		if u > update {
+			update = u
+		}
+	}
+
+	return Etag(md5Counts, update)
+}