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/plugin_valid_test.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsValidPluginId(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]bool{
+		"":    false,
+		"a":   false,
+		"ab":  false,
+		"abc": true,
+		"abcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghij":  true,
+		"abcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghijabcdefghij1": false,
+		"../path":     false,
+		"/etc/passwd": false,
+		"com.mattermost.plugin_with_features-0.9": true,
+		"PLUGINS-THAT-YELL-ARE-OK-2":              true,
+	}
+
+	for id, valid := range testCases {
+		t.Run(id, func(t *testing.T) {
+			assert.Equal(t, valid, IsValidPluginId(id))
+		})
+	}
+}