v3-ndc-sdk-typescript: config to switch connector header used for service auth checks

### Component

c/v3-ndc-sdk-typescript

### Is your proposal related to a problem?

I want to forward a Authorization header used in Hasura auth to the connector for a downstream api to use, but the connector reserves the use of Authorization header for its own authn checks

### Describe the solution you'd like

connector configuration to allow specifying an alternative header for the connector's own authn checks.

This would for example allow it to use x-hasura-token: abc123, and therefore allow the forwarding of the Authorization header to the connector's functions

### Describe alternatives you've considered

Patching the library at npm install to do the same as described.

Sending the authentication token twice in different headers or function parameters isn't exactly acceptable.

Start in c/v3-ndc-sdk-typescript by locating the connector configuration and the service-auth header handling. Confirm how the current Authorization header is selected, then define completion as allowing an alternative configured header while preserving Authorization for forwarding to connector functions.

Written by the indexing model from the issue text.