getCalendarProperty (url, property, defaultValue) {
		for (const calendar of this.config.calendars) {
			if (calendar.url === url && calendar.hasOwnProperty(property)) {
				return calendar[property];
			}
		}

		return defaultValue;
	}
Helper method to retrieve the property for a specific calendar url.
@param {string} url The calendar url
@param {string} property The property to look for
@param {string} defaultValue The value if the property is not found
@returns {*} The property