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/user_access_token_test.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUserAccessTokenIsValid(t *testing.T) {
+	ad := UserAccessToken{}
+
+	appErr := ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.id.app_error")
+
+	ad.Id = NewRandomString(26)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.token.app_error")
+
+	ad.Token = NewRandomString(26)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.user_id.app_error")
+
+	ad.UserId = NewRandomString(26)
+	require.Nil(t, ad.IsValid())
+
+	ad.Description = NewRandomString(256)
+	appErr = ad.IsValid()
+	require.False(t, appErr == nil || appErr.Id != "model.user_access_token.is_valid.description.app_error")
+}