ZEVA2 - credit transfer actions

Create actions associated with credit transfers. These actions should include (but are not limited to):

(1) Creating a credit transfer
(2) Updating a transfer's status (e.g. DRAFT -> SUBMITTED_TO_SUPPLIER, SUBMITTED_TO_SUPPLIER -> APPROVED_BY_SUPPLIER, etc.)
(3) Issuing a transfer (i.e. updating its status to ISSUED (or whatever the final status is), creating an associated zevUnitTransaction, sending emails to subscribed parties, etc.)

If certain actions relies on features that are not yet implemented in zeva2, you can use placeholders/comments.

Please remember to call auth() and use the information returned to determine if a user is allowed to perform a certain action; if you are unsure what the logic should be, you can just do what you think is reasonable and refine it later after receiving user feedback.