Password reset mail not using user's language

[scf-wgross]

Steps to reproduce

1. Enter wrong password and then press password reset button
2. Receive password reset link via e-mail

Expected behaviour

E-mail should use user's language

Actual behaviour

E-mail uses instead default language (as acquired from browser?)

Server configuration

Operating system:
OpenLeap 42.2

Web server:
Apache 2.4.23-8.3.1

Database:
Maria-DB 10.0.29-18.1

PHP version:
php 7.0.7-14.3.1

Nextcloud version: (see Nextcloud admin page)
11.0.2

Updated from an older Nextcloud/ownCloud or fresh install:
Fresh install

Where did you install Nextcloud from:
OpenSuse repository

Signing status:

Signing status

Login as admin user into your Nextcloud and access 
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

App list

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

Nextcloud configuration:

Config report

If you have access to your command line run e.g.:
sudo -u www-data php occ config:list system
from within your Nextcloud installation folder

or 

Insert your config.php content here. 
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

Are you using external storage, if yes which one: local/smb/sftp/...
No

Are you using encryption: yes/no
No

Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...
No

Client configuration

Browser:
Mozilla Firefox 53.0

Operating system:
Windows 7 Pro 64bit

Logs

No relevant entries in these log files

[MorrisJobke]

cc @nickvergessen haven't you fixed this for 11?

[scf-wgross]

User's language is used with share links sent by e-mail, but then the user is already logged in.

[nickvergessen]

Well it uses the browsers language, since the user is not logged in. We can of course change it and use the language the potential user had selected. But not really a but for me.

[nickvergessen]

We can easily change the language of the actual text, however there is currently no option to set the language for the header/footer stuff.

[scf-wgross]

Well, you're right, it's really not such a big thing. It stems from our rather special situation of a lab with people speaking different languages sharing a local PC to access their data.