### What?
Unable to add collections to the config dynamically if they reference
their own collection in a relationship field.
This was discovered while working on the folder view feature which
dynamically adds collections to your config if it is enabled per
collection.
### Why?
When `sanitizeCollection` runs, it takes the current config. If you are
sanitizing a collection before adding it to the config, that collection
cannot have any self referencing relationship fields on it otherwise it
fails the validRelationships check.
### How?
Using a reducer we now initialize the validRelationships variable with
the incoming collection slug.
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