Support "Field Selection" for Visma.net Financials API Endpoints when fetching data

[Yıldırım]

In order to be able to avoid returning a payload with full DTO that might be no use for the clients, "select" / "Fields" etc. operator should be exposed via the endpoints so that the Endpoint returns only the specified fields. In this way, unnecessary traffic caused in the transactions can be circumvented.

E.g.

GET .../GeneralLedgerTransactions?select=fields.batchNumber,fields.endingBalance

Example Case:
As an API Client we only need the field, 

 "lastModifiedDateTime": "2021-06-25T12:18:10.118Z"

from the GeneralLedgerTransactions Endpoint.

We maintain over 1100 different companies on Visma.net and would like to know which ones are actively are being used. I've already got a script working, but it seems like an awful waste of computing power to check for the MAXIMUM lastModifiedDateTime in each customer Dataset. 

E.g.

/controller/api/v1/GeneralLedgerTransactions?ledger=werkelijk&fromPeriod=201801&toPeriod=202106&pageNumber=1&pageSize=1?fields=lastModifiedDateTime

Ref: Selecting fields in GET-request