Use this API to retrieve the public configuration required to enter an
acquired card through the TabaPay Browser SDK.

Purpose: Load the Browser SDK from sdkUrl and initialize it using
browserClientId before collecting card information.

Browser SDK flow:

1. Call GET /v1/externalcards/configuration.
2. Load the Browser SDK using sdkUrl.
3. Initialize the SDK using browserClientId.
4. Capture card information through the Browser SDK.
5. Receive a short-lived cardToken from the SDK.
6. Submit the token to POST /v1/clients/{clientId}/externalcards.
7. Read clientId and resourceId from the successful response.

Raw card information must be entered through the provider's Browser SDK
and must not be sent directly to the Mbanq API.

Behaviour: A successful response contains only public Browser SDK
configuration values.