Global refactoring of the project to use poetry and implement tests,

fixing bugs, changing the handling of dto and db models, preparing to
add new functionality

library_service/settings.py

@@ -0,0 +1,52 @@
+import os
+from dotenv import load_dotenv
+from fastapi import FastAPI
+from sqlmodel import create_engine, SQLModel, Session
+from toml import load
+
+load_dotenv()
+
+with open("pyproject.toml") as f:
+    config = load(f)
+
+# Dependency to get the FastAPI application instance
+def get_app() -> FastAPI:
+    return FastAPI(
+        title=config["tool"]["poetry"]["name"],
+        description=config["tool"]["poetry"]["description"],
+        version=config["tool"]["poetry"]["version"],
+        openapi_tags=[
+            {
+                "name": "authors",
+                "description": "Operations with authors.",
+            },
+            {
+                "name": "books",
+                "description": "Operations with books.",
+            },
+            {
+                "name": "relations",
+                "description": "Operations with relations.",
+            },
+            {
+                "name": "misc",
+                "description": "Miscellaneous operations.",
+            }
+        ]
+    )
+
+USER = os.getenv("POSTGRES_USER")
+PASSWORD = os.getenv("POSTGRES_PASSWORD")
+DATABASE = os.getenv("POSTGRES_DB")
+HOST = os.getenv("POSTGRES_SERVER")
+
+if not USER or not PASSWORD or not DATABASE or not HOST:
+    raise ValueError("Missing environment variables")
+
+POSTGRES_DATABASE_URL = f"postgresql://{USER}:{PASSWORD}@{HOST}:5432/{DATABASE}"
+engine = create_engine(POSTGRES_DATABASE_URL, echo=True, future=True)
+
+# Dependency to get a database session
+def get_session():
+    with Session(engine) as session:
+        yield session