chore: rework DB module (#324)

src/fastapi_toolsets/__init__.py

@@ -7,16 +7,19 @@ Example usage:
     from fastapi import FastAPI, Depends
     from fastapi_toolsets.exceptions import init_exceptions_handlers
     from fastapi_toolsets.crud import CrudFactory
-    from fastapi_toolsets.db import create_db_dependency
+    from fastapi_toolsets.db import Database
     from fastapi_toolsets.schemas import Response
 
+    db = Database("postgresql+asyncpg://postgres:postgres@localhost/app")
+
     app = FastAPI()
+    db.install(app)
     init_exceptions_handlers(app)
 
     UserCrud = CrudFactory(User)
 
     @app.get("/users/{user_id}", response_model=Response[dict])
-    async def get_user(user_id: int, session = Depends(get_db)):
+    async def get_user(user_id: int, session = Depends(db)):
         user = await UserCrud.get(session, [User.id == user_id])
         return Response(data={"user": user.username}, message="Success")
 """