Edit Page (BookEditPath) function not working for multilanguage projects

[Rojax]

The Edit this page button in the footer does not work for multi-language projects. It always points to a single content. Either to .Site.Params.contentDir (if set) or to /content by default.

This can be reproduced using a config such as

defaultContentLanguage: en
defaultContentLanguageInSubdir: true
languages:
  en:
    contentDir: content/en
    disabled: false
    languageCode: en-US
    languageDirection: ltr
    languageName: English
    title: My Book
    weight: 10
  de:
    contentDir: content/de
    disabled: false
    languageCode: de-DE
    languageDirection: ltr
    languageName: Deutsch
    title: My Book
    weight: 20

See also: gohugoio/hugo#11237