Multi-value Custom Fields for External ID Arrays

Currently, Front's custom fields only support single string values, which creates a significant limitation when managing conversations that need to reference multiple external identifiers.

Our system frequently handles conversations that relate to multiple external entities (Tickets).
Currently, we're limited to storing one external ID per custom field, which doesn't scale for conversations involving numerous related items(Tickets).

Expected Behavior:

• Custom fields should accept arrays of strings as input

• UI should provide an interface to add/remove multiple values

• API should support passing arrays in custom field values

• Search and filtering should work across all values in the array