Multi language support

[MartinPontius]

Implement multi-language support.

• Copenhagen app: Danish and English
• Rhine Erft app: German and English
• Danube app: German, Hungarian and English

[MartinPontius]

Some OPT packages don't support specific languages. This leads to the following error for Hungarian in the Zala app:

[plugin:pioneer:codegen] Package '@open-pioneer/authentication' requires messages for locale 'hu'. Either update the package or add messages from the app via 'overrides'.

A solution might be to add the missing texts from the packages in the hu.yaml file.