feat: expose useMutationState for optimistic updates

[danilofuchs]

Describe the feature you'd like to request

Optimistic updates in React Query 5 can be simpler by using the useMutationState anywhere in the application to hook into a running mutation state and variables

https://tanstack.com/query/latest/docs/framework/react/guides/optimistic-updates#via-the-ui

Describe the solution you'd like to see

I would love if tRPC exposed a api.createPost.useMutationState() hook

Describe alternate solutions

1. I could use useMutationState() on my own and reconstruct the mutation key, but I understand this is an implementation detail and not exposed by tRPC
2. This API could be exposed in the apiUtils realm: apiUtils.createPost.mutationState()

Additional information

No response

👨‍👧‍👦 Contributing

• 🙋‍♂️ Yes, I'd be down to file a PR implementing this feature!

Funding

• You can sponsor this specific effort via a Polar.sh pledge below
• We receive the pledge once the issue is completed & verified

[JonParton]

Just FYI the generated query key is exposed using the getQueryKey() helper just for this kind of use!

I'll leave for others to comment on including to the trpc api itself!