[iOS] Issue for PrimaryEnrollment data getting

[rnr]

The current iOS implementation fails when the primary rate has a non-null audit_access_expires parameter in the data, because the decoder cannot directly convert a String Date to a Data object.
An error occurs when doing so:
typeMismatch(Swift.Double, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "primary", intValue: nil), CodingKeys(stringValue: "audit_access_expires", intValue: nil)], debugDescription: "Expected to decode Double but found a string instead.", underlyingError: nil))
and all the courses to view in the Gallery Dashboard are not displayed

Expected behaviour:
All courses and the primary course should be displayed in the Gallery Dashboard whether audit_access_expires is set or not