`Transaction`

Represents a monetary transaction for a particular user.

field	type	required	description
`transaction_id`	integer	-	UID for this transaction
`user_id`	integer	yes	(Internal) id of the user making the transaction.
`user`	`User`	-	User making the transaction.
`amount`	integer	yes	Amount of currency added to the user's account. May be negative.
`description`	string	yes	Description of this transaction.
`reference`	string?	no	Optional reference string.
`created_at`	timestamp	-	Timestamp at which this transaction was performed. Cannot be set or modified.

POST /transactions
- Create and return a new Transaction.
- Note that unlike other models containing a User, creation of a new User with a Transaction is not supported. Ensure the user exists before creating the transaction.
GET /transactions
- Get all Transactions matching the given parameters.
- Supported filter parameters:
  - transaction_id
  - user_id
  - description
  - reference
  - created_before
  - created_after
GET /transactions/{transaction_id}
- Get the Transaction for the given transaction_id
PATCH /transactions/{transaction_id}
- Not supported, Transactions are considered immutable.
DELETE /transactions/{transaction_id}
- Not supported. Transactions cannot be individually deleted.
- Note that if the User is deleted then the all their Transactions will also be deleted.
- To reset or set a User's balance, submit a Transaction which changes it to the desired value.
* /transactions/{transaction_id}/user
- Inherits all routes from /users/{user_id} with the associated user_id.