Do we need behaviours?

The example is using behaviours to define the structure of the API interface:
https://github.com/dwyl/phoenix-ecto-append-only-log-example/blob/e8eee00fab8f1555ab93c2d2757c497207d81873/lib/append/append_only_log.ex#L9-L14

The implementation of the API is then done in the `before_compile` macro:
https://github.com/dwyl/phoenix-ecto-append-only-log-example/blob/e8eee00fab8f1555ab93c2d2757c497207d81873/lib/append/append_only_log.ex#L25-L48
...
However I'm not sure behaviours are needed for the append only example.
From my understanding it makes sense to use behaviours when multiple modules need to provide the same functions but with a different logic of implemention. In our example only the `AppendOnlyLog` module is implementing the behaviours.

For a learning purpose it makes sense to see how behaviours works :+1: but I'm not sure if they provide a lot of values for this repository?

Should we still keep them to demonstrate how they can be used?

ref: https://elixir-lang.org/getting-started/typespecs-and-behaviours.html#behaviours