dao-marketplace/#45: collection stats

[austinmilt]

This PR adds three new fields to the Collection object to support collection display in the marketplace.

Usage

{
  collectionsFeaturedByMarketCap(orderDirection:DESC, startDate:"2020-07-04T17:06:10Z", endDate: "2022-08-22T17:06:10Z", limit:5, offset: 0){
    floorPrice
    nftCount
    listedCount
    volumeTotal(startDate:"2022-07-04T17:06:10Z", endDate:"2022-08-22T17:06:10Z")
    holderCount
  }
}

Changes

• added query and field for total volume of sales, with time range args (collections.rs, nft.rs)
• added query and field for count of current holders of collection NFTs, which throws an error if the collection isnt found (collections.rs, nft.rs)
• added query and field for count of active listings of collection NFTs, which throws an error if the collection isnt found (collections.rs, nft.rs)

[austinmilt]

Fine for speed writing the queries as sql strings but doing them through diesel dsl helps ensure further updates don't break the query as the type system validates the queries. I think all these queries are supported by diesel.

Great point! I was thinking I needed GROUP BY which diesel doesnt support, but since it's just a single collection, the GROUP BY shouldnt be necessary. I'll refactor