### What?
Fixes the issue with `in` querying when the collection has a join field.
### Why?
When using `.aggregate`, MongoDB doesn't cast a comma delimited value
for the `$in` operator to an array automatically as it's not handled by
Mongoose.
### How?
Sanitizes the incoming value to an array if it should.
Fixes https://github.com/payloadcms/payload/issues/8901
7a7a2f3918