已上线:生产1.20.6/测试1.20.6b0。 Requires application AK/SK and independent user:authenticate Scope. JSON body only: username is the full employee email; password is not trimmed. Returns the same eight basic fields as the employee directory. Unknown, inactive, ambiguous accounts and incorrect passwords all return 401 INVALID_CREDENTIALS. Never issues or updates employee tokens, password hashes or sign-in metadata. Fixed-window limits per minute: 60/application and 10/email across applications by default. HTTPS and server-to-server calls only; never put credentials in URLs.