consolidate database transactions when creating new thread

backend/main.py

@@ -36,6 +36,7 @@ async def get_posts(db: db_dependency):
 
 @app.post('/', status_code=status.HTTP_201_CREATED)
 async def create_thread(db: db_dependency, data: PostCreate):
+    try:
         # Create the post
         post = Post(
             author=data.author,
@@ -43,7 +44,7 @@ async def create_thread(db: db_dependency, data: PostCreate):
             content=data.content
         )
         db.add(post)
-    db.commit()
+        db.flush()
 
         # Create the thread
         thread = Thread(
@@ -52,7 +53,7 @@ async def create_thread(db: db_dependency, data: PostCreate):
             content=post.content
         )
         db.add(thread)
-    db.commit()
+        db.flush()
 
         # Update the Post with thread_id
         post.thread_id = thread.id
@@ -64,6 +65,9 @@ async def create_thread(db: db_dependency, data: PostCreate):
             'title': post.title,
             'content': post.content
         }
+    except Exception as e:
+        db.rollback()
+        raise HTTPException(status_code=400, detail=str(e))
 
 
 @app.get('/{thread_id}', status_code=status.HTTP_200_OK)
@@ -95,7 +99,7 @@ async def create_reply(db: db_dependency, data: PostCreate, thread_id: int = Pat
             'content': post.content
         }
 
-    raise HTTPException(404, f'Could not find thread')
+    raise HTTPException(status_code=404, detail='Could not find thread')
 
 
 @app.get('/catalog', status_code=status.HTTP_200_OK)