Add Json field support

config.toml

@@ -10,3 +10,7 @@ email = "string"
 
 [Events.page_viewed]
 path = "string"
+
+[Events.event_foo]
+name = "string"
+data = "json"

internal/property/json.go

@@ -0,0 +1,28 @@
+package property
+
+import (
+	"database/sql/driver"
+	"encoding/json"
+	"fmt"
+)
+
+type Json struct{}
+
+func newJson(args []string) (typeInterface, error) {
+	if len(args) > 0 {
+		return nil, fmt.Errorf("invalid arguments: %q", args)
+	}
+	return Json{}, nil
+}
+
+func (j Json) ColumnType() string {
+	return "json"
+}
+
+func (j Json) ConvertValue(v interface{}) (driver.Value, error) {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return nil, fmt.Errorf("value is not json: %v", v)
+	}
+	return b, nil
+}

internal/property/type.go

@@ -38,6 +38,7 @@ var types = map[string]func([]string) (typeInterface, error){
 	"date":        newDate,
 	"datetime":    newDateTime,
 	"decimal":     newDecimal,
+	"json":        newJson,
 }
 
 func (t2 *Type) UnmarshalText(text []byte) error {