Verify provider credentials at the client constructor

Do not assume similarly named provider credentials are interchangeable. For each SDK or API integration, trace the client constructor to the exact configuration value it consumes, including trimming, fallbacks, and environment-specific branches. Verify a credential against the client and operation that use it; a key accepted by one service from the same provider does not establish that another client reads or accepts it. Recheck current source and configuration documentation because routing can change.