Retrieve transactions.

The following criteria can be used to filter the results:

• By Citizens
  A citizen can be specified by either a `citizenId` or `externalRef` or by both a `citizenId` and `externalRef`. If both a `citizenId` and `externalRef` are supplied they must both resolve to the same citizen.
  
• By date range
  "A transaction `before` (exclusive of) a given date, or `since` (inclusive) of a given date or transactions `since` and `before` the given dates" +
• By Pagination
  Results can be paginated by supplying a `limit` and or an `offset`.
  The `offset` is zero or a positive integer that controls the number of transactions to skip before returning transactions while the `limit` is a positive integer value that controls the size of the page to be returned.
  If the request does not filter by a citizen, pagination will be enforced, with a default `limit` and `offset` used if these values are not provided.

Note that if `citizenId` and `externalRef` are not provided, pagination will be enforced, with default values for `limit` and `offset` being used if none are provided.