[date] Find booking date overlap

Booking date checker: start & end = guest wish date.
Must NOT overlap with any known availability start-end periods.

Code:

start-end is exactly the same as non-availability start-end
OR
start-end is within the range as non-availability start-end

start is within the range as non-availability start-end

end is within the range as non-availability start-end

https://pastebin.com/cjYSAGf5