As I can see, in the visa checkout documentations we can pass an externalClientID to transfer the payments to specified merchant(externalClientID).
Also in the Visa Chekout API Explorer, I can see that we can update or read a client under the "Relationship" tab. But how a client is added into my profile? Or How I can add a client? In the documentation, the line is stated "Typically, the external client ID is assigned by a partner; however, Visa Checkout assigns a value if one is not specified". Who is the partner is reffered to as? Or when visa checkout will assign a value itself? infact I am looking forward to implement a multi vendor system and I need to add my users as my clients so that they should be able to receive the payment. Is that even possible?
This is a question about a Partner account, generally these individuals are banks, financial institutions, or the equivalent of a reseller for a gateway. They would be a large organization, which organization are you representing?
The feature you are referring to also is present on all Developer accounts, this allows the child accounts to link themselves to a larger parent account. You'll have to have the organization name, and be able to define the relationship and attach themselves as a client to the parent organization you create. This is not a commonly used feature, but if you wish to set this up for your client, you can practice in the developer center.
Lastly you are also referring to payments. Visa Checkout does not process payments in any way, the customer will need a relationship with a Merchant Services Provider outside of Visa Checkout. I would encourage the you to first setup an account with an MSP, and most likely not worry about VCO, or setting up a parent/child relationship in VCO, as it will not be necessary, as it wouldn't be needed for payment management, only to be able to manage users/security keys.
Does this help?
Really thankful for your reply!
The information is quit helpful, but this does not fit in my scenario. As stated in my previous question, I am developing a multi vendor system, in which any user can be buyer and seller at the same time. So any buyer should has the ability to send the payment to any seller. So, I can not make every seller my partner. So what API would you suggest me, in any will work in my scenario?
I don't think we currenlty have any APIs for your use case.