Feature request: Add field for OSCAR designation

Amateur radio satellites get an OSCAR designation assigned by AMSAT.

E.g. Navy-OSCAR 84 (short: NO-84) was assigned to ParkinsonSAT/PSat (NORAD ID 40654) (see List of all OSCAR designation).

Currently we store the OSCAR designation in the 'alternative names' field of a satellite. To make it easier to cross-reference, it could be nice to add an optional field oscar_designation to the satellite model where either the short or full OSCAR designation is stored. This will allow the OSCAR designation to be shown where desirable (and where showing the full list of alternative names is not sensible), see issue satnogs-network#424.