I think the important thing is to be consistent. I worked with a microservice system for years (as a front end engineer) where some teams would use 404 to indicate record not found, some teams would use your system, and a couple teams sent back the response in the header! Of the teams using your system it would quite an ordeal to find out the meaning of "status: 1000", especially if the system was 10+ years old and the original team no longer around.
Fair points. My APIs have an associated constants classes/header files to define all these values.
So long as you have the source you are fine - and if you (or the third party/maintainer) don’t have the source then it doesn’t matter the approach because there will be bugs you can’t fix throughout the service.
