config updated to improve setting values, writing changes and test coverage

internal/config/section_test.go

@@ -301,3 +301,12 @@ func TestSetValueValidator(t *testing.T) {
 		t.Errorf("nested setValue(bad) = %v; want errRejected", err)
 	}
 }
+
+// parseString handles string fields too, although convert assigns a string
+// to a string field before reaching it.
+func TestParseStringString(t *testing.T) {
+	v, err := parseString("text", reflect.TypeOf(""))
+	if err != nil || v.Interface() != "text" {
+		t.Errorf("parseString(text, string) = %v, %v", v, err)
+	}
+}