Add public getAccessToken() methods to expose OAuth2 tokens from client credentials#214

Copilot wants to merge 2 commits intomainopenfga/java-sdk:mainfrom

copilot/fix-b8160508-0f80-42a8-8309-d42eb5341eabopenfga/java-sdk:copilot/fix-b8160508-0f80-42a8-8309-d42eb5341eabCopy head branch name to clipboard