add order book endpoint

stock/proto/stock.proto

@@ -8,6 +8,43 @@ service Stock {
 	rpc Quote(QuoteRequest) returns (QuoteResponse) {}
 	rpc Price(PriceRequest) returns (PriceResponse) {}
 	rpc History(HistoryRequest) returns (HistoryResponse) {}
+	rpc OrderBook(OrderBookRequest) returns (OrderBookResponse) {}
+}
+
+message Order {
+	// the asking price
+	double ask_price = 2;
+	// the bidding price
+	double bid_price = 3;
+	// the ask size
+	int32 ask_size = 4;
+	// the bid size
+	int32 bid_size = 5;
+	// the UTC timestamp of the quote
+	string timestamp = 6;
+}
+
+// Get the historic order book and each trade by timestamp
+message OrderBookRequest {
+	// stock to retrieve e.g AAPL
+	string stock = 1;
+	// the date in format YYYY-MM-dd
+	string date = 2;
+	// optional nanosecond timestamp start
+	int64 start = 3;
+	// optional nanosecond timestamp end
+	int64 end = 4;
+	// limit number of prices
+	int32 limit = 5;
+}
+
+message OrderBookResponse {
+	// the stock symbol
+	string symbol = 1;
+	// date of the request
+	string date = 2;
+	// list of orders
+	repeated Order orders = 3;
 }
 
 // Get the last price for a given stock ticker