Missing implementation for std::vector<std::optional<std::string>>

[gelldur]

When want to receive multiple keys and keys may be not present.
If I use vector<string> then it will fail if at least 1 key is missing.

	std::map<std::string, std::string> result;
	boost::redis::request req;

	req.push_range("MGET", keys.begin(), keys.end());
	boost::redis::response<std::vector<std::optional<std::string>>> res;

	exec(req, res);

error: no matching function for call to 'boost_redis_from_bulk'
include/boost/redis/adapter/detail/adapters.hpp:387:7: note: in instantiation of function template specialization 'boost::redis::adapter::detail::vector_impl<std::vector<std::optional<std::basic_string<char>>>>::operator()<std::basic_string_view<char>>' requested here

When using: boost::redis::response<std::optional<std::vector<std::string>>> res;
It will mismatch number of expected responses.

[mzimbres]

Thanks for reporting, I will have a look at it soon.