Allow arrays with runtime defined rank.

[1uc]

Arrays do not need to have a compile-time constant number of dimensions (rank). There's two compile-time constant variable:

HighFive/include/highfive/bits/H5Inspector_misc.hpp

Lines 165 to 166 in 1299c55

	static constexpr size_t ndim = 0;
	static constexpr size_t recursive_ndim = ndim;

It's uses seems to be mostly for input validation
https://github.com/search?q=repo%3ABlueBrain%2FHighFive%20recursive_ndim&type=code

Here it's not immediately used for input validation, and there's no container near by to get he runtime-value:

HighFive/include/highfive/bits/H5ReadWrite_misc.hpp

Lines 132 to 143 in 1299c55

	template <typename T>
	template <class F>
	BufferInfo<T>::BufferInfo(const DataType& dtype, F getName, Operation _op)
	: op(_op)
	, is_fixed_len_string(dtype.isFixedLenStr())
	// In case we are using Fixed-len strings we need to subtract one dimension
	, n_dimensions(details::inspector<type_no_const>::recursive_ndim -
	((is_fixed_len_string && is_char_array) ? 1 : 0))
	, data_type(
	string_type_checker<char_array_t>::getDataType(create_datatype<elem_type>(), dtype)) {
	// We warn. In case they are really not convertible an exception will rise on read/write
	if (dtype.getClass() != data_type.getClass()) {

[1uc]

Marked as v3 since it requires changes to the internal inspector. Given how close we are to v3 and that users have touch this internal detail to add new containers, we might as well consider changes to the inspector as breaking changes.

[1uc]

Fixed by #938.