By Jonathan Saul LONDON (Reuters) – Insurers have raised the cost of providing cover for merchant ships through the Black Sea, adding to soaring rates to transport goods through the region for vessels still willing to sail after Russia’s invasion of Ukraine. Ship owners pay annual war-risk insurance cover as well as an additional “breach” premium when entering high-risk areas. These separate premiums are calculated according to the value of the ship, or hull, for a seven-day period. Ship insurers have quoted the additional premium rate for seven days at anywhere between 1% to 2% and up to 5% o…