Steps to reproduce

1. Edit travel site (via Resource app "travel-demo/sites/travel.yaml")
2. Add new language to the site (for example es)
3. Go to pages app and open "travel" page for editing
4. New language is not visible in language selector in pages editor
5. Open edit dialog of any component on page
6. New language is not visible in language selector in dialog

Expected results

Locale changes in site definition are visible in info.magnolia.ui.field.LocaleSelector without need of restarting the instance.

Actual results

Instance needs to be restarted for info.magnolia.ui.field.LocaleSelector to reflect changes

Development notes

This is most likely side effect of making sites registry https://jira.magnolia-cms.com/browse/MGNLSITE-105
In definition app you can see that site definition contains all the locale changes, but they are not reflected in ui. LocaleContext, SiteManger, or some other component is probably not correctly refreshed after changes in site definition.