Within a solution app a field shall denote to a user within organisation (member directory).

Currently such field exists "Assiged To".

However, it allows selecting only org members that have any access to the solution (permissions). The field in question should work by allowing selecting member in member directory, even those who do not know existence of the solution, that they are being tagged.

This could be either a new field, e.g., Referred To.

Or it can be "Assiged To" field, which allows to enable such behavior once "Disable assignment notifications" is on.