feat: implement extractor error handling and batch processing for MSSQL and Postgres

internal/app/etl/extractor/main.go

@@ -0,0 +1,36 @@
+package extractor
+
+import (
+	"context"
+	"sync"
+
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/custom_errors"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
+)
+
+type Extractor interface {
+	ProcessBatch(
+		ctx context.Context,
+		tableInfo config.SourceTableInfo,
+		columns []models.ColumnType,
+		chunkSize int,
+		batch models.Batch,
+		indexPrimaryKey int,
+		chChunksOut chan<- models.Chunk,
+		rowsRead *int64,
+	) error
+
+	Exec(
+		ctx context.Context,
+		tableInfo config.SourceTableInfo,
+		columns []models.ColumnType,
+		chunkSize int,
+		chBatchesIn <-chan models.Batch,
+		chChunksOut chan<- models.Chunk,
+		chErrorsOut chan<- custom_errors.ExtractorError,
+		chJobErrorsOut chan<- custom_errors.JobError,
+		wgActiveBatches *sync.WaitGroup,
+		rowsRead *int64,
+	)
+}