Move LocalizedValueTest into dedicated file

tests/data.py

@@ -0,0 +1,13 @@
+from django.conf import settings
+
+
+def get_init_values() -> dict:
+    """Gets a test dictionary containing a key
+    for every language."""
+
+    keys = {}
+
+    for lang_code, lang_name in settings.LANGUAGES:
+        keys[lang_code] = 'value in %s' % lang_name
+
+    return keys