* A utility function which checks if two date ranges overlap.
*
* @param {Object} givenPeriodLeft - the first period to compare.
* @param {Object} givenPeriodRight - the second period to compare.
* @returns {Object} { overlap: number of days the overlap is present, overlapStartDate: the start date of the overlap in time format, overlapEndDate: the end date of the overlap in time format }
* @throws {Error} Uncaught Error: Invalid period
*
* @example
* getOverlappingDaysInPeriods(
* { start: new Date(2021, 0, 11), end: new Date(2021, 0, 13) },
* { start: new Date(2021, 0, 11), end: new Date(2021, 0, 14) }