ms2/share modal improvements

[FelipeTrost]

Summary

I only managed to implement the changes for the link share modal described in #259.
I also fixed some bugs along the way.

Details

• Process page throws UnauthorizedError -> correct error message on client
• fix for legacy-store: parse dates of processes, which were being stored as strings and needed to be parsed again after reading them.
• process-documentation: The function called in the effect was mutating the state array and then calling setState with that array, since the array is still the same array (pointer), no rerender was triggered. This cause a part of the ducmentation to be missing until you triggered another rerender somehow (by resizing the screen for example).
• documentation-page: creatorId is not defined on legacy store, so I just used optional chaining to avoid the error.