This PR makes it so Zed staff can use a separate Anthropic API key for
the LLM service.
We also added an `is_staff` column to the `usages` table so that we can
exclude staff usage from the "active users" metrics that influence the
rate limits.
Release Notes:
- N/A
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Co-authored-by: Max <max@zed.dev>
This PR puts the initial infrastructure for the LLM service's database
in place.
The LLM service will be using a separate Postgres database, with its own
set of migrations.
Currently we only connect to the database in development, as we don't
yet have the database setup for the staging/production environments.
Release Notes:
- N/A
