Update lib.rs

[falyhery]

• Implement section entry definitions
• Implement section CRUD methods
• Implement content entry definitions
• Implement content CRUD methods

[e-nastasia]

All looks good to me!
I also have an update here on the code structure and how can be the same thing done a bit differently. I only realized it while already in the devcamp: I decided to move the get_latest_entry function implementation into the corresponding handlers section to have lib.rs be only an API definition that doesn't really contain any implementation details. This is just a matter of taste and it doesn't change anything in the code correctness. You can see what I meant in this commit.