Answer
Yes, OData/REST is still the recommended integration approach regardless of whether Aurena's UI itself is actually being used — OData being documented alongside Aurena reflects that it's the same underlying API layer the UI consumes, not that it's somehow Aurena-UI-specific or unsuitable for pure backend integration. On whether a new custom attribute automatically appears in a projection: it depends entirely on how that specific projection is implemented. If the projection's entity set uses the standard entity without restricting it to a specific subset of attributes, new attributes do flow through automatically; if the entity has been overridden in that projection to expose only a fixed, limited set of attributes, new attributes won't appear until the projection itself is updated to include them. In practice, the majority of standard projections don't apply that kind of attribute restriction, so new custom attributes usually do show up automatically.