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/permalink.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type Permalink struct {
+	PreviewPost *PreviewPost `json:"preview_post"`
+}
+
+type PreviewPost struct {
+	PostID             string      `json:"post_id"`
+	Post               *Post       `json:"post"`
+	TeamName           string      `json:"team_name"`
+	ChannelDisplayName string      `json:"channel_display_name"`
+	ChannelType        ChannelType `json:"channel_type"`
+	ChannelID          string      `json:"channel_id"`
+}
+
+func NewPreviewPost(post *Post, team *Team, channel *Channel) *PreviewPost {
+	if post == nil {
+		return nil
+	}
+	return &PreviewPost{
+		PostID:             post.Id,
+		Post:               post,
+		TeamName:           team.Name,
+		ChannelDisplayName: channel.DisplayName,
+		ChannelType:        channel.Type,
+		ChannelID:          channel.Id,
+	}
+}