SIP-217 add asset details for futures markets (Synthetixio#1750)

* Add assets details to futuresmarket.
- This will enable consumers to know what catergory the market belong too, ie. is forex etc

* Make asset key consistent.
I'm sure there's a reason why this is the case, but I'll add this commit for some discussion

* Revert "Make asset key consistent."

This reverts commit 0b743c8.

* Add logic to adjust futures market with incorrect asset key format

Author: 0xjocke

index.js

@@ -438,7 +438,19 @@ const getFuturesMarkets = ({
 	if (!fs.existsSync(pathToFuturesMarketsList)) {
 		return [];
 	}
-	return JSON.parse(fs.readFileSync(pathToFuturesMarketsList));
+	const futuresMarkets = JSON.parse(fs.readFileSync(pathToFuturesMarketsList)) || [];
+	return futuresMarkets.map(futuresMarket => {
+		/**
+		 * We expect the asset key to not start with an 's'. ie. AVAX rather than sAVAX
+		 * Unfortunately due to some historical reasons 'sBTC', 'sETH' and 'sLINK' does not follow this format
+		 * We adjust for that here.
+		 */
+		const marketsWithIncorrectAssetKey = ['sBTC', 'sETH', 'sLINK'];
+		const assetKeyNeedsAdjustment = marketsWithIncorrectAssetKey.includes(futuresMarket.asset);
+		const assetKey = assetKeyNeedsAdjustment ? futuresMarket.asset.slice(1) : futuresMarket.asset;
+		// mixin the asset details
+		return Object.assign({}, assets[assetKey], futuresMarket);
+	});
 };
 
 /**