last-modified attribute should not be rejected on authoritative updates

[mxsasha]

IRRD automatically adds the last-modified attribute on authoritative objects since #290. However, when submitting changes to objects, IRRD rejects this attribute as it's unknown. This makes sense as it's not a "real" RPSL attribute, but IRRD should just replace the value. This is potentially very confusing for users.

For rpki-ov-state (#270) we probably already discard it silently, but should double check.

[rubenskuhl]

Thanks for that @mxsasha . Have you confirmed that rpki-ov-state is being silently discarded ?

[mxsasha]

Thanks for that @mxsasha . Have you confirmed that rpki-ov-state is being silently discarded ?

Yes, set here for route for example, and there are also tests for this.

It's a bit different from last-modified, because rpki-ov-state is always relative to this specific IRRD instance, whereas last-modified is relative to the RPSL database/source. So for last-modified we accept and keep the value from a mirror, for rpki-ov-state we do not.