v0.27.0 baseUrl -> url function issue #1613

Describe the bug
All links on the web page have been changed to http

Steps To Reproduce
Steps to reproduce the behavior:

1. Clone release branch (or download release archive 0.27.0)
2. Server on nginx(https) -> docker(http) proxy
3. when access to home page, all links changed to http
   browser warning https site but load http resource

Expected behavior
all resource load fine

Screenshots

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): 0.27.0
• 443 - nginx -> 80 nginx+php-fpm docker

Additional context
Previously, the way to get url was to call baseUrl. In this distribution, it is changed to url function. It seems to be related to this.

.env content
APP_URL=https://wiki.seq.kr