provide initial versions of zone endpoints

These are only examples for now and nothing serious yet but showcase the
innards of query and types for now.

It is a beginning.

zone_create.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+
+	"dim/types"
+)
+
+// Creates a new DNS zone.
+func zoneCreate(c *Context, req Request, res *Response) error {
+	zoneName := new(types.ZoneName)
+	if err := req.Parse(&zoneName); err != nil {
+		res.AddMessage(LevelError, "expected zone name, but got error: %s", err)
+		return nil
+	}
+	id := 0
+	err := c.tx.
+		QueryRow(`insert into zones(name, created_by, modified_by)
+				values ($1, $2, $2) returning id`, zoneName, c.username).
+		Scan(&id)
+	if err != nil {
+		res.AddMessage(LevelError, "could not create zone")
+		return fmt.Errorf("could not create zone '%s': %s", zoneName, err)
+	}
+	return nil
+}

zone_list.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"fmt"
+
+	"dim/query"
+	"dim/types"
+)
+
+type (
+	ZoneListOptions struct {
+		Attributes types.FieldList `json:"attributes"`
+	}
+)
+
+var (
+	zoneListMap = map[string]string{
+		"name":        "z.name",
+		"modified_by": "z.modified_by",
+		"modified_at": "z.modified_at",
+		"created_by":  "z.modified_by",
+		"created_at":  "z.modified_at",
+	}
+)
+
+func zoneList(c *Context, req Request, res *Response) error {
+	options := ZoneListOptions{
+		Attributes: types.NewFieldList("name"),
+	}
+	if err := req.ParseAtLeast(0, &options); err != nil {
+		res.AddMessage(LevelError, "could not parse options: %s", err)
+		return nil
+	}
+
+	selClause := query.FieldListToSelect(options.Attributes, zoneListMap)
+
+	rows, err := c.tx.Query(fmt.Sprintf(`select %s from zones z`, selClause))
+	if err != nil {
+		res.AddMessage(LevelError, "could not return result")
+		return fmt.Errorf("could not get zone list: %s", err)
+	}
+	defer rows.Close()
+	res.Result["zones"], err = query.RowsToMap(rows)
+	if err != nil {
+		delete(res.Result, "zones")
+		res.AddMessage(LevelError, "could not return result")
+		return fmt.Errorf("could not parse zone list: %v", err)
+	}
+	return nil
+}