Agent identity: Agents that act and appear as themselves

This post introduces and details the 'agent identity' feature for Glean's agent orchestration platform. Previously, agents borrowed the identity of the user invoking them, leading to issues with access control (too broad or too narrow) and audit trails. The new agent identity feature allows agents to act through their own service account credentials, creating a distinct bot/account for each agent across integrated systems like Slack, Jira, and GitHub. This decouples agent invocation from agent permissions, ensures consistent access, and provides proper attribution in audit trails by recording actions under the agent's own account. This also resolves issues with long-running or scheduled agents that were previously hampered by expiring user access tokens.