As a Wikipedia editor, I want to get //all// labels of a Wikidata item, in order to be able to describe an item not just in the content language of my wiki, but also in several other minority languages it covers.
**Problem:**
Wikidata includes support for several custom language codes, by setting `$wmgExtraLanguageNames` in [InitialiseSettings.php](https://gerrit.wikimedia.org/r/plugins/gitiles/operations/mediawiki-config/+/4ed028b5f86c12f15255596deb0d8e5de5927ac2/wmf-config/InitialiseSettings.php#21617) (warning, large file, may slow down your browser). However, those language codes are only defined for Wikidata (test and real) and Commons; on client wikis, Wikibase does not consider them to be valid, and therefore refuses to return labels in those languages, even if they’re defined on Wikidata. See discussion on [Wikidata:Project_chat#Kven](https://www.wikidata.org/wiki/Wikidata:Project_chat#Kven)
**Example:**
Swedish Wikipedia would like to use the smj label of [Tysfjord (Q493851)](https://www.wikidata.org/wiki/Q493851), or the fkv label of [Porsanger (Q483885)](https://www.wikidata.org/wiki/Q483885). The following work snippets work in a [Lua sandbox on Wikidata](https://www.wikidata.org/wiki/Module:Blank?action=edit#mw-scribunto-console), but not in a [Lua sandbox on Swedish Wikipedia](https://sv.wikipedia.org/wiki/Module:Blank?action=edit#mw-scribunto-console):
```lang=lua
=mw.wikibase.getLabelByLang( 'Q493851', 'smj' )
=mw.wikibase.getLabelByLang( 'Q483885', 'fkv' )
```
**Screenshots/mockups:**
**BDD**
GIVEN
AND
WHEN
AND
THEN
AND
**Acceptance criteria:**
* [ ] Labels in languages from $wmgExtraLanguageNames can be used on client wikis
**Open questions:**