UI language (and other) fields

[vbohata]

Summary

Application/UI interface fields for capturing UI language, locale and maybe more.

Motivation:

During the application issue resolv. it is useful to know in which language the application UI has been displayed. The typical use case: multi language web application sometimes performing bad only in specific language or returning errors only for specific language (because of missing translations, ...).

Detailed Design:

Probably not best to be included under user_agent fields. I would also avoid nesting it under http fields as the Accepted language and Content Language can actually differ from what the user actually gets. The UI fields could be useful for both application and OS or host fields.

So something like:

ui.language
ui.locale
ui.type
...

Nested to:

application.ui.language = Czech
application.ui.locale = cs_CZ.UTF-8
application.ui.type = Browser

Useful for OS:

os.ui.language = Czech
os.ui.type = Console

[kgeller]

@vbohata since these fields would be fairly new territory for ECS, I think they'd be best suited as an RFC.