Use traits and derive macros for the common model functionality

[KevinCLydon]

Most of the modules in the models module have a lot of functions in common where the only differences are the structs. It would save a lot of time and consolidate a lot of code if we could switch a lot of that over to use traits and derive macros. For example, a lot of those modules have a find_by_id function. We could create a trait called FindableById and write a derive macro to generate the code for it.