Issue types (and other "constants") are not translated in REST

The issue type names and descriptions are not translated in REST. Steps to reproduce:

• translate JIRA as per this documentation (e.g. in French)
• set your user language to French
• view an issue. the issue type is translated
• view an issue through the REST API. the issue type is not translated Unable to embed resource: rest.png of type image/png

This applies equally to other constants that can be translated.