Add server skeleton with directory app and local dev loop

internal/data/data.go

@@ -0,0 +1,42 @@
+// Package data provides tabular app data sources.
+package data
+
+import (
+	"encoding/csv"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+type Source interface {
+	Table(app, name string) ([]map[string]string, error)
+}
+
+type Dir struct {
+	Root string
+}
+
+func (d Dir) Table(app, name string) ([]map[string]string, error) {
+	f, err := os.Open(filepath.Join(d.Root, app, name+".csv"))
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	rows, err := csv.NewReader(f).ReadAll()
+	if err != nil {
+		return nil, err
+	}
+	if len(rows) == 0 {
+		return nil, fmt.Errorf("table %s/%s has no header row", app, name)
+	}
+	header := rows[0]
+	records := []map[string]string{}
+	for _, row := range rows[1:] {
+		record := map[string]string{}
+		for i, column := range header {
+			record[column] = row[i]
+		}
+		records = append(records, record)
+	}
+	return records, nil
+}