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/file_info_test.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	_ "image/gif"
+	_ "image/png"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFileInfoIsValid(t *testing.T) {
+	info := &FileInfo{
+		Id:        NewId(),
+		CreatorId: NewId(),
+		CreateAt:  1234,
+		UpdateAt:  1234,
+		PostId:    "",
+		Path:      "fake/path.png",
+	}
+
+	t.Run("Valid File Info", func(t *testing.T) {
+		assert.Nil(t, info.IsValid())
+	})
+
+	t.Run("Empty ID is not valid", func(t *testing.T) {
+		info.Id = ""
+		assert.NotNil(t, info.IsValid(), "empty Id isn't valid")
+		info.Id = NewId()
+	})
+
+	t.Run("CreateAt 0 is not valid", func(t *testing.T) {
+		info.CreateAt = 0
+		assert.NotNil(t, info.IsValid(), "empty CreateAt isn't valid")
+		info.CreateAt = 1234
+	})
+
+	t.Run("UpdateAt 0 is not valid", func(t *testing.T) {
+		info.UpdateAt = 0
+		assert.NotNil(t, info.IsValid(), "empty UpdateAt isn't valid")
+		info.UpdateAt = 1234
+	})
+
+	t.Run("New Post ID is valid", func(t *testing.T) {
+		info.PostId = NewId()
+		assert.Nil(t, info.IsValid())
+	})
+
+	t.Run("Empty path is not valid", func(t *testing.T) {
+		info.Path = ""
+		assert.NotNil(t, info.IsValid(), "empty Path isn't valid")
+		info.Path = "fake/path.png"
+	})
+}
+
+func TestFileInfoIsImage(t *testing.T) {
+	info := &FileInfo{}
+	t.Run("MimeType set to image/png is considered an image", func(t *testing.T) {
+		info.MimeType = "image/png"
+		assert.True(t, info.IsImage(), "PNG file should be considered as an image")
+	})
+
+	t.Run("MimeType set to text/plain is not considered an image", func(t *testing.T) {
+		info.MimeType = "text/plain"
+		assert.False(t, info.IsImage(), "Text file should not be considered as an image")
+	})
+}