You can either add a new language or change a default one.
By default the application supports two languages. English and Swedish. The default languages are stored in \..\application\resources\web\assets\locales. The default languages files are called: en.json and sv.json. Note: Do NOT change the languages files in this location. The next upgrade will replace your updated files with new ones.
Let say you like to add Norwegian as a new language to this application.
Verify that you have an overlay folder specified in the main Module of the application. "overlay_dir": "/config/resources_external/overlays",
In the overlays folder. Create a folder called assets (\config\resources_external\overlays\assets)
In the asset folder, create a folder called locales (\config\resources_external\overlays\assets\locales)
Add the en.json file from default location and rename the file to no.json. Update all the keys in the file to Norwegian.
Create a file in the asset folder called ui_config_overrides.json. Add the following content to the file:
The result should look like: Note that we do not have an fortified_logo.svg, see line 4 above. Add a file if you like a logo.
Restart the service and verify
You like to change a text line of one of the default languages to something else. This only apply to languages shipped with product, right now Swedish and English.
Copy the language(s) you like to change from \..\application\resources\web\assets\locales
Create a folder in \config\resources_external\overlays\assets\ called custom_locales. Paste the languages files there.
Remove all keys except the ones you like to change.
Update the text to your liking.
Restart the service and verify
The file and folder structure should look like: