[jravani]

Refs #8.

A transformer node can now carry grid_import_price and grid_export_price in EUR/kWh. They set the import and export price of its trade{grid_$k} in EUR/MWh, and a feed-in price also limits export to the transformer rating. A node without them translates exactly as before: 300 EUR/MWh import and an unpaid export sink.

Example, a 400 kVA transformer with "grid_import_price": 0.34, "grid_export_price": 0.079:

"grid_trafo_9": {
  "node": "ntrafo_9",
  "carrier": "electricity",
  "import": {"price": 340, "limit": 0.4},
  "export": {"price": 79, "limit": 0.4}
}

Changes:

• config/enerplanet-to-meme.json: transformer trade rules, mapping version 1.6.0 (1.5.0 is the PV parasitic efficiency on the base branch).
• pkg/t1k/mapping_test.go: TestMappingGridPrices covers a node with both prices, the reverse restoring them, and a node without them.
• docs/mappings/enerplanet-to-meme.md and CHANGELOG.md: the field table and the entry.

Checks:

• TestMappingGridPrices fails without the mapping change (import.price = 300, want 340; export.price missing) and passes with it.
• make test-race, go vet and gofmt pass.
• make golden-update leaves the golden files unchanged: the example payload carries no prices.

[jravani]

Verdict: ready to merge into jay/enerplanet-integration; no blockers.

go test -race ./... passes at 8139d75, and forward and reverse runs on the example with prices added match the PR description.

Non-blocking:

• suggestion: an explicit import price of 0.30 EUR/kWh is not restored by reverse (config line 178)
• question: a zero feed-in price caps export at the rating, a missing one does not (config line 181)