fix(cors): allow cross-origin API calls only from configured origins

[danilovid]

No description provided.

[torkel-hoge]

instead of having such utility func we can add a new type implementing flag.Value (see docs) to this package

it can be something like:

type StringList []string

func (l *StringList) String() string {
	return strings.Join(*l, ",")
}

func (l *StringList) Set(v string) error {
	for _, s := range strings.Split(v, ",") {
		if s = strings.TrimSpace(s); s != "" {
			*l = append(*l, s)
		}
	}
	return nil
}

there's a generic version as well, but imo it's too complicated, since we should explicitly pass a parsing function:

Example

type List[T any] struct {
	Values []T
	Parse  func(string) (T, error)
}

func (l *List[T]) String() string {
	if l == nil || len(l.Values) == 0 {
		return ""
	}
	parts := make([]string, len(l.Values))
	for i, v := range l.Values {
		parts[i] = fmt.Sprint(v)
	}
	return strings.Join(parts, ",")
}

func (l *List[T]) Set(s string) error {
	for _, raw := range strings.Split(s, ",") {
		v, err := l.Parse(strings.TrimSpace(raw))
		if err != nil {
			return fmt.Errorf("incorrect value %q: %w", raw, err)
		}
		l.Values = append(l.Values, v)
	}
	return nil
}