Basic Digest and Authentication in Amazon SNS

My purpose is to fan out messages to HTTPS endpoint from SNS topic. I have my backend code in spring-boot and I have enabled Basic Authentication to secure my endpoint.

Let's say the URL to which I will be posting message from SNS Topic is

https:abcd.com/test

Credentials are:

Username: user

Password: password

While subscribing this endpoint what URL shall I mention in SNS topic?

Should it be:

https:user:password@abcd.com/test

or it should be something else?

I've read the official aws doc but it wasn't clear to me. I also read somewhere that you can't add any additional headers in the POST request that SNS will send. In that case, how will the Authorization header be added? Kindly help.