feat: add useLoginSettings hook [LIBS-516]

[tomzemp]

Implements LIBS-516

This runtime hook helps with building of custom login apps. See notes on dhis2/ui#1395 for more description of other changes needed / context of custom login apps.

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Key features

1. Adds hook useLoginSettings which populates public information related to login app settings from auth/loginConfig and locales/ui (note that these endpoints are not created/made public), so currently dummy values are just being populated.

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Description

The hook useLoginSettings is added. This hook would only be populated for login app types, and hence depends on changes in app-platform.

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Checklist

• Have written Documentation
  • this is a draft PR for deciding how to structure login app. More documentation will be added if we actually implement this hook.
• Has tests coverage
  • See above: tests will be implemented if we decide we want to implement this hook.

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Known issues

• note that endpoints have not been implemented, so the hook is just using dummy values for now.

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Screenshots

n/a

[tomzemp]

this is a separate query because it does not need to be refetched