suggestions from omar: provide a default value for price_sources by m…

…aking it an opiton field

mm2src/mm2_main/src/lp_ordermatch/simple_market_maker.rs

@@ -137,10 +137,10 @@ impl PriceSources {
 #[derive(Deserialize)]
 pub struct StartSimpleMakerBotRequest {
     cfg: SimpleMakerBotRegistry,
-    // TODO: We can't `flatten` the price_sources while implementing `default` because of this issue:
-    // https://github.com/serde-rs/serde/issues/1626 - so let's only flatten for now and provide no default.
+    // TODO: This is marked as an `Option` for now so we can be able to provide a default value for it since
+    // `flatten` & `default` don't work together: https://github.com/serde-rs/serde/issues/1626.
     #[serde(flatten)]
-    price_sources: PriceSources,
+    price_sources: Option<PriceSources>,
     bot_refresh_rate: Option<f64>,
 }
 
@@ -752,7 +752,7 @@ pub async fn start_simple_market_maker_bot(ctx: MmArc, req: StartSimpleMakerBotR
             *state = RunningState {
                 trading_bot_cfg: req.cfg,
                 bot_refresh_rate: refresh_rate,
-                price_urls: req.price_sources.get_urls(),
+                price_urls: req.price_sources.unwrap_or_default().get_urls(),
             }
             .into();
             drop(state);

mm2src/mm2_main/tests/mm2_tests/lp_bot_tests.rs

@@ -32,7 +32,6 @@ fn test_start_and_stop_simple_market_maker_bot() {
              "mmrpc": "2.0",
              "method": "start_simple_market_maker_bot",
              "params": {
-                "price_url": "https://prices.komodian.info/api/v2/tickers",
                 "cfg": {
                     "KMD-BEP20/BUSD-BEP20": {
                         "base": "KMD-BEP20",