How to invoke a REST OIC integration from BIP by a data source where OIC is in Fusion domain

Summary:

We are invoking a REST integration from BIP by a data source using Basic auth which is working fine in our Dev environment.
But In our Test environment oic is created in Fusion domain, where we are not able to invoke a REST integration using Basic auth. Getting 401: Unauthorized error.
Error:
Error while processing authentication at Trigger. Failed due to - 401 : Unauthorized
Can someone please help in providing the solution.

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