Add Pit file stability fee event

- file event on the pit contract is overloaded and each implementation
  logs a note
- existing Pit file transformer now specified as dealing with ilks

pkg/transformers/pit_file/stability_fee/repository.go

@@ -0,0 +1,48 @@
+package stability_fee
+
+import (
+	"github.com/vulcanize/vulcanizedb/pkg/core"
+	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
+)
+
+type Repository interface {
+	Create(headerID int64, model PitFileStabilityFeeModel) error
+	MissingHeaders(startingBlockNumber, endingBlockNumber int64) ([]core.Header, error)
+}
+
+type PitFileStabilityFeeRepository struct {
+	db *postgres.DB
+}
+
+func NewPitFileStabilityFeeRepository(db *postgres.DB) PitFileStabilityFeeRepository {
+	return PitFileStabilityFeeRepository{
+		db: db,
+	}
+}
+
+func (repository PitFileStabilityFeeRepository) Create(headerID int64, model PitFileStabilityFeeModel) error {
+	_, err := repository.db.Exec(
+		`INSERT into maker.pit_file_stability_fee (header_id, what, data, tx_idx, raw_log)
+        VALUES($1, $2, $3, $4, $5)`,
+		headerID, model.What, model.Data, model.TransactionIndex, model.Raw,
+	)
+	return err
+}
+
+func (repository PitFileStabilityFeeRepository) MissingHeaders(startingBlockNumber, endingBlockNumber int64) ([]core.Header, error) {
+	var result []core.Header
+	err := repository.db.Select(
+		&result,
+		`SELECT headers.id, headers.block_number FROM headers
+               LEFT JOIN maker.pit_file_stability_fee on headers.id = header_id
+               WHERE header_id ISNULL
+               AND headers.block_number >= $1
+               AND headers.block_number <= $2
+               AND headers.eth_node_fingerprint = $3`,
+		startingBlockNumber,
+		endingBlockNumber,
+		repository.db.Node.ID,
+	)
+
+	return result, err
+}