Add /exchanges endpoint to list available exchanges

tests/rpc/test_rpc_apiserver.py

@@ -1578,6 +1578,38 @@ def test_api_strategy(botclient):
     assert_response(rc, 500)
 
 
+def test_api_exchanges(botclient):
+    ftbot, client = botclient
+
+    rc = client_get(client, f"{BASE_URI}/exchanges")
+    assert_response(rc)
+    response = rc.json()
+    assert isinstance(response['exchanges'], list)
+    assert len(response['exchanges']) > 20
+    okx = [x for x in response['exchanges'] if x['name'] == 'okx'][0]
+    assert okx == {
+        "name": "okx",
+        "valid": True,
+        "supported": True,
+        "comment": "",
+        "trade_modes": [
+            "spot",
+            "isolated futures",
+        ]
+    }
+
+    mexc = [x for x in response['exchanges'] if x['name'] == 'mexc'][0]
+    assert mexc == {
+        "name": "mexc",
+        "valid": True,
+        "supported": False,
+        "comment": "",
+        "trade_modes": [
+            "spot",
+        ]
+    }
+
+
 def test_api_freqaimodels(botclient, tmpdir, mocker):
     ftbot, client = botclient
     ftbot.config['user_data_dir'] = Path(tmpdir)
@@ -1933,3 +1965,4 @@ def test_api_ws_send_msg(default_conf, mocker, caplog):
 
     finally:
         ApiServer.shutdown()
+        ApiServer.shutdown()