refactor(agentex): Slack gateway reads bot credentials from env, not DB

[michael-chou359]

What

The Slack gateway acts as one fixed identity — a dedicated bot service account, not a per-user proxy — so its credentials (signing secret, bot token, acting API key + account) are static, app-level values. This moves them out of the throwaway agent_api_keys DB store and into env / k8s-secret, where static deployment secrets belong.

Why

The DB store only ever existed as a bridge toward per-user, per-request secrets that vary by user and can't live in static pod env (the code itself called it a "THROWAWAY store — plaintext … To be replaced by sgp-secrets user-scope"). With the gateway settled as a single bot identity, that justification is gone: these are one-per-deployment secrets, so the environment's secret is the right home. It also gets plaintext secrets out of the application database and removes the DB read path entirely.

Changes

• Drop _gateway_secret and the DB-store name constants; _fetch_bot_token, _fetch_signing_secret, and _acting_identity read env directly.
• Rename the acting identity user → bot (SLACK_GATEWAY_ACTING_BOT_API_KEY) to reflect that the bot is its own entity, not the invoking user.
• Remove the now-unused get_by_name_and_type repository method.
• Update unit tests to the env-based reads.

Deploy note

The gateway now reads four env vars — SLACK_SIGNING_SECRET, SLACK_BOT_TOKEN, SLACK_GATEWAY_ACTING_BOT_API_KEY, SLACK_GATEWAY_ACCOUNT_ID — from the deployment secret. They must be present in an environment's secret before this rolls out there.

Testing

• 73 passed (gateway + delegation-header unit tests), ruff clean.

🤖 Generated with Claude Code

Greptile Summary

The PR moves the Slack gateway’s fixed bot credentials from the database to deployment environment secrets and removes the obsolete repository lookup. It also closes the previously reported missing-identity path by refusing to dispatch without a bot API key when authorization is enabled.

• Reads the signing secret, bot token, bot API key, and account ID from environment-backed deployment secrets.
• Fails closed when the bot API key is absent in an authorization-enabled environment.
• Removes the unused agent-agnostic API-key repository method and updates unit tests for environment-based credential loading.

Confidence Score: 5/5

The PR appears safe to merge because the previously reported unauthenticated-dispatch path now aborts before dispatch when authorization is enabled.

No blocking failure remains.

Important Files Changed

Filename	Overview
agentex/src/domain/use_cases/slack_gateway_use_case.py	Replaces database-backed gateway secret reads with environment-backed bot credentials and adds the required fail-closed identity guard.
agentex/src/domain/repositories/agent_api_key_repository.py	Removes the now-unused agent-agnostic credential lookup method.
agentex/tests/unit/use_cases/test_slack_gateway_use_case.py	Updates credential tests for direct environment reads and covers both fail-closed and local-development missing-key behavior.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Slack turn] --> B[Read bot identity from environment]
  B --> C{Bot API key present?}
  C -- Yes --> D[Verify API key and account headers]
  D --> E[Resolve target and dispatch as bot principal]
  C -- No --> F{Authorization enabled?}
  F -- Yes --> G[Abort turn without dispatch]
  F -- No --> H[Local development bypass]

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_{Reviews (2): Last reviewed commit: "fix(agentex): Slack gateway fails closed..." | Re-trigger Greptile}