Say I have a `StorageDoubleMap` that stores `Data` structs for each user and `ContextId`
```rust
	#[pallet::storage]
	pub type Info<T: Config> = StorageDoubleMap<
		_,
		Blake2_128Concat,
		T::AccountId,
		Twox64Concat,
		T::ContextId,
		Data,
	>;
```
Is there an option to limit the amount of entries per `AccountId`? Or should I keep a count of entries in a separate map?