AccountName shouldn't be required

[whatsthecraic]

It shouldn't be mandatory to specify the AccountName in the azure connection string:

auto storage_account_name_pos = connection_string.find("AccountName=");
if (storage_account_name_pos == std::string::npos) {
	throw InvalidInputException("A invalid connection string has been provided.");
}

It's not required by the Azure API and the connection string can be used to specify different settings, e.g. the blob endpoint or the SAS token.

I think the error message is also too generic: A invalid connection string has been provided. => why is it invalid?

CC @quentingodeau , author of the snippet according to git blame