feat(query-core): add queryClient argument to mutation callbacks and mutationFn

[raymondanythings]

Background

When working with mutations, most callback logic (optimistic updates, cache updates, invalidations) needs direct access to queryClient.

Currently, this requires manually calling useQueryClient() inside callbacks, or wrapping mutation logic with custom hooks, which adds boilerplate.

PR #9193 proposes passing queryClient via MutationFunctionContext, but this changes callback parameter structures and may break compatibility with existing code.

What’s Different in This PR

Instead of replacing the last argument with a context object, this PR appends queryClient as the final parameter in:

• mutationFn
• onMutate
• onSuccess
• onError
• onSettled

This preserves all existing parameters and their positions, making it fully backward-compatible for users who don’t use the new argument.

Example Usage

useMutation({
  mutationFn: (variables, queryClient) => {
    return api.updateItem(variables).then(res => {
      queryClient.invalidateQueries({ queryKey: ['items'] })
      return res
    })
  },
  onSuccess: (data, variables, _context, queryClient) => {
    queryClient.setQueryData(['items'], prev => [data, ...(prev ?? [])])
  }
})

Why This Approach

Backward-compatible: Does not alter existing argument order.

Low migration cost: Existing code works without changes.

Simple mental model: queryClient is always the last argument.