fixed version prometheus-client

added env variable SPOOLMAN_METRICS_ENABLED for enabled database collector

set metrics path as /metrics

checked Null values at vendors, init weight and price
removed some logs

pyproject.toml

@@ -20,6 +20,7 @@ dependencies = [
     "psycopg2-binary~=2.9",
     "setuptools~=68.0",
     "WebSockets>=11.0.3",
+    "prometheus-client>=0.20.0",
 ]
 requires-python = ">=3.9"