Missing filter for Multireference fields

[MarkoStrassl]

The CRM event collection uses a multireference field named "Related To" to link events to various entities like Accounts, Leads, Contacts, and Opportunities. Currently, there's no filtering option available for this field, hindering efficient event search and management.

Desired functionality:

1. Implement a filter mechanism for the "Related To" multireference field.
2. Allow users to select specific entities (e.g., Accounts, Opportunities) and filter events associated with those selections.
3. Support selecting multiple entities simultaneously.

Benefits:

1. Enhanced search capabilities: Users can efficiently find events related to specific entities.
2. Improved event management: Filtering by related entities streamlines identifying and managing relevant events.