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/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
+}