Fix: locale on new group role selection

What does this MR do and why?

The current select options for roles were rendered by the predefined enum roles in model/user with titleize method, this MR uses a map to match the role key with a localized label, for presenting to the users.

/cc @prajnamas @orozot @qk44077907

Screenshots or screen recordings

Since there were no translations for these keys at present, there will not have screenshots for before and after.

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

1. Go to your GDK.
2. Click on the + button on the navbar and choose Create New Group
3. On the page, go to Role section and click on the dropdown.
4. Observe.

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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