Sharingd wants to use the “Local Items keychain

While Keychain Access and the iCloud Keychain is specific to the Mac and iOS, there are other applications such as 1Password and LastPass which have various syncing options (Windows, iOS, Android, Linux, and even web-based) so you would never be without access to your passwords.

It's a private framework made by Apple to interface with iCloud documents and files.

It's safe to allow and there's a possibility of keychain corruption if it won't stick (and since you wouldn't normally get that warning unless the automated process to save your iCloud password has hit a bump like having keychain items deleted or expiring)

From https://discussions.apple.com/thread/6684809

Back up all data before proceeding.

Launch the Keychain Access application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Keychain Access in the icon grid.

Select the login keychain from the list on the left side of the Keychain Access window. If your default keychain has a different name, select that.

If the lock icon in the top left corner of the window shows that the keychain is locked, click to unlock it. You'll be prompted for the keychain password, which is the same as your login password, unless you've changed it.

Right-click or control-click the login entry in the list. From the menu that pops up, select
Change Settings for Keychain "login"

In the sheet that opens, uncheck both boxes, if not already unchecked.
From the menu bar, select
Keychain Access ▹ Preferences ▹ First Aid

If the box marked
Keep login keychain unlocked
is not checked, check it.
Select
Keychain Access ▹ Keychain First Aid
from the menu bar and repair the keychain.

Quit Keychain Access.