Make local fields a bit more standard

[alifemove]

I'd love for local fields to move a bit.

As an aggregator we are transitioning several hundred data sources to RESO and all of them have different local fields, without knowing the DD extremely well we can't tell what is a local field and what is a RESO standard field during mapping, mapping updates, looking through the data, etc.. Additionally publishing this data is difficult because we can't expect stakeholders to know which fields are RESO and can be relied upon and which are not so we can't really include the data at all even though it might be useful.

Could the local fields be moved into a LocalFields object within whatever resource they are associated with?

Property: {
    ListingKey: abcd3,
    ModificationTimestamp: 1234,
    LocalFields: {
        DistanceToVolcano: 5ft
   }
}