We have a guy on our team who loves the shiny new thing, but lots of times you can get it working in a much easier, more understandable way.
For azure functions, a separate repo may make sense. I would probably do that, but I also suggest not putting much logic at all in the azure functions. For example, this:
- When the function is executed, drop a document here
- ... write this db record
- ... execute some job somewhere ...
- ... call an API ...
Is a good use of azure functions. Keep it "functional!"
Bad uses are "systems" implemented in Azure functions. As soon as you feel like you need to use or even MIGHT need to use code in your main codebase, please, don't use azure functions! :)