index donations/claims/transfers on any currency

[vibern0]

An easy way would be to have a Map<K,V>, but since this is not possible, having an array of an abject is also doable.

Something like contributions: [AssetContributions!] @derivedFrom(field: "entity") on a given entity, and

type AssetContributions @entity {
  id: ID!
  asset: Bytes!
  amount: BigDecimal!
  entity: dont-know-yet!
}

see impactMarket/smart-contracts-dao#91 for reference