Error:  Error: SuperTokens core threw an error for a POST request to path: '/public/recipe/session' with status code: 400 and message: Field name 'userId' is invalid in JSON input

    at Querier.sendRequestHelper (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/querier.js:361:27)
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Querier.sendPostRequest (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/querier.js:81:40)
    at async Object.createNewSession (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/recipe/session/sessionFunctions.js:55:20)
    at async Object.createNewSession (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/recipe/session/recipeImplementation.js:98:28)
    at async Object.createNewSessionInRequest (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/recipe/session/sessionRequestFunctions.js:388:21)
    at async Function.createNewSession (/home/aadimch/Desktop/pos/api/node_modules/supertokens-node/lib/build/recipe/session/index.js:48:16)

Not sure why I am getting this error? I am doing this

const userId = user.user_id;
const recipe = supertokens.convertToRecipeUserId(userId)
await Session.createNewSession(req, res, "public", recipe);