PURE invariant: (ProviderID, IdentityValue) must be unique. Returns the error when existingCount other rows already use this value on the provider, else null.
(ProviderID, IdentityValue)
existingCount
null
PURE invariant:
(ProviderID, IdentityValue)must be unique. Returns the error whenexistingCountother rows already use this value on the provider, elsenull.