How to get a single record endpoint based on custom value instead of Id

Summary:

I am trying to create an endpoint for a business object where I want to get the record based on a selfmade field InvoiceNumber (Number) instead of the default Primary key Id?

How can I achieve this?

I found the following link but this seems like a very complex way to achieve this, could it be implemented easier?

https://blogs.oracle.com/vbcs/post/service-methods-for-business-objects-in-visual-builder

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