Date Intervals for Inventory Module

[RealDekkia]

Is your feature request related to a problem? Please describe.
With a lot of help from MightyMCoder I implemented a field-type to store date intervals for inventory items: MightyMCoder/InventoryManager#86
The new version 5.0.0 has a built-in inventory manager that looks similar to the one by MightyMCoder, but without that feature.

Describe the solution you'd like
A way to store time intervals for regular inspection of inventory items, like in InventoryManager by MightyMCoder.

Describe alternatives you've considered
Staying on Admidio 4.x.x

[MightyMCoder]

@RealDekkia:
This field type is planned for the next release version of admidio.

I didn't find the time to implement it for the 5.0 release.

[RealDekkia]

Amazing, thanks.