Move GET id functions in all BE controllers

[mcgarrye]

After adding a new GET endpoint to the listings path, it was discovered that paths with GET /:id can cause errors if the function is not at the bottom of the file as is recommended by NestJS documentation.
https://docs.nestjs.com/controllers#route-parameters

AC:

• Update all controllers in the BE to have the GET id functions at the bottom of the file.
• Update Readme/best practices documentation to include this as a standard