Created genre table and added links and endpoints for it.

library_service/models/db/__init__.py

@@ -1,14 +1,17 @@
 from .author import Author
 from .book import Book
+from .genre import Genre
 from .links import (
     AuthorBookLink, GenreBookLink,
     AuthorWithBooks, BookWithAuthors,
-    GenreWithBooks, BookWithAuthorsAndGenres
+    GenreWithBooks, BookWithGenres,
+    BookWithAuthorsAndGenres
 )
 
 __all__ = [
-    'Author', 'Book',
+    'Author', 'Book', 'Genre',
     'AuthorBookLink', 'AuthorWithBooks',
     'BookWithAuthors', 'GenreBookLink',
-    'GenreWithBooks', 'BookWithAuthorsAndGenres'
+    'GenreWithBooks', 'BookWithGenres',
+    'BookWithAuthorsAndGenres'
 ]

library_service/models/db/genre.py

@@ -9,6 +9,6 @@ if TYPE_CHECKING:
 class Genre(GenreBase, table=True):
     id: Optional[int] = Field(default=None, primary_key=True, index=True)
     books: List["Book"] = Relationship(
-        back_populates="authors",
+        back_populates="genres",
         link_model=GenreBookLink
     )