Protocol for data into their snapshot representations.

Snapshots can only be printable string content or it won't be great for getting compared by humans / in git.

Example

defmodule TestStruct do
  defstruct value: <<1, 2, 3>>

  defimpl GitSnapshot.Snapshot do
    def to_string(struct) do
      Base.encode16(struct.value)
    end
  end
end