*_metadata() functions do not clear the users cache

[ryan]

The 'users' cache includes metadata for each user. When metadata is updated for the 'user' meta_type, the metadata functions should clear the users cache.

[ryan]

(In [14179]) Clear the users cache when updating user metadata. fixes #13075

[scribu]

Maybe those checks would have been better placed in update_user_meta() ...

[scribu]

use hooks to delete user cache

[nacin]

Maybe those checks would have been better placed in update_user_meta() ...

I think I disagree. I would think that metadata functions should work exactly like the user, post, and comment wrappers. Thus, any object-specific code should be in the metadata API.

That said, I like using hooks. That also leads me to thinking about #11254.

[ryan]

None of our clean cache functions are on hooks. Any cleaning customizations should be done from hooks within the cleaners, I think. The current method is good enough for 3.0.