Metadata oracle endpoint in Yoroi

Cardano metadata oracles (nut.link) are the first generation of oracles providing external data sources to the blockchain, that the developers can use.

Yoroi backend is used by multiple wallets, such as Yoroi, Atomic and others. Currently, Yoroi backend doesn't have the capability for fetching metadata from oracle endpoints. https://github.com/Emurgo/yoroi-graphql-migration-backend/

We want to implement a new Yoroi backend endpoint that will provide the metadata oracles datapoints.

Please note, this proposal has been accepted in Fund 3, but ended up being over budget.

## Deliverables
We will implement and propose a change to Yoroi backends that will introduce a new endpoint will enable wallet developers to:

• Fetch the metadata oracles data points
• Filter by the time of the datapoint
• Filter the datapoints by a list of trusted oracles
• Filter by a datapoint ticker (ADATC, ADAUSD…)
• Filter by the source of a ticker (coingecko, cryptoconpare, Ergo…)

We will implement this with the first 3 months of receiving the budget.

## Relevant experience
We have experience with oracles on UTXO blockchains. We launched the first metadata oracle on Cardano, and we were the first community public oracle pool on Ergo blockchain.

Five Binaries is an infrastructure development company. We're Cardano pioneers - with the first Cardano block minted on an aeroplane, first stake pool on the ITN and the first Shelley transaction on the mainnet.

We are trusted by customers such as Emurgo, Trezor or Cardano Foundation. To get in touch or find more information about us, please visit https://fivebinaries.com/.

## Budget
We estimate it will take us 10 engineering-hours to complete the deliverables.

Our rate, which comprises of our engineers' salaries, infrastructure costs, office rent, accounting and taxes is 100 EUR per hour.

We pay our people well, because they are both skilled and exceptionally experienced in the industry. And last but not least, because we respect them and want them to feel good and appreciated while working on Cardano.