Implement generic Prebid bid param override rules

.env.example

@@ -40,6 +40,11 @@ TRUSTED_SERVER__INTEGRATIONS__PREBID__ENABLED=false
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__SERVER_URL=https://prebid-server.com/openrtb2/auction
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__TIMEOUT_MS=1000
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__BIDDERS=kargo,rubicon,appnexus
+# TRUSTED_SERVER__INTEGRATIONS__PREBID__BID_PARAM_OVERRIDES='{"bidder-name":{"param1":12345,"param2":"value"}}'
+# Compatibility env shape for bidder -> zone -> params overrides
+# TRUSTED_SERVER__INTEGRATIONS__PREBID__BID_PARAM_ZONE_OVERRIDES='{"kargo":{"header":{"placementId":"_abc"}}}'
+# Preferred canonical env shape for future generic rules
+# TRUSTED_SERVER__INTEGRATIONS__PREBID__BID_PARAM_OVERRIDE_RULES='[{"when":{"bidder":"kargo","zone":"header"},"set":{"placementId":"_abc"}}]'
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__AUTO_CONFIGURE=false
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__DEBUG=false
 # TRUSTED_SERVER__INTEGRATIONS__PREBID__TEST_MODE=false