fix: preserve existing refresh_token when server omits it in refresh response#2304

ctonneslan wants to merge 1 commit intomodelcontextprotocol:mainmodelcontextprotocol/python-sdk:mainfrom

ctonneslan:fix/preserve-refresh-token-on-refreshctonneslan/python-sdk:fix/preserve-refresh-token-on-refreshCopy head branch name to clipboard