PoC for persistent messages in Drafts

[danjoa]

1. Replace hard-coded checks by @mandatory annotations → BAD generic error messages: ⇒ Fiori should add localized field labels

2. Create new Travel → SAVE → all fields with missing input are marked red:


   

   BTW: we should get rid of duplicate input field for currency

3. Fill in missing description → all missing input indicators are gone:


   

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Note: intentionally doing that on an old JavaScript branch