ROADMAP of Covers-API

Compatibility with other database backend.

Compatible with postgresql/sqlite

Add other covers providers

Google Books
https://developers.google.com/books/docs/viewer/developers_guide
Internet Archive https://archive.org/developers/index-apis.html?highlight=book
ISBND
https://isbndb.com/apidocs

Write better documentation

Step by step installation
auto generated openapi
comment for every method

Code organization

Put caching behind a feature, make uses optional even if compiled with.
separate backend logic into library
add units tests