Command provided to the Bazel daemon: `run`, `test`, `build`, `coverage`, `mobile-install`, ...

`gcs` (Google Cloud Storage), `aws_s3`, or `disk`.

Cache backend: `gcs` (Google Cloud Storage), `aws_s3`, or `redis`.

TODO(bduffany): Document the difference between `miss` and `upload` Cache event type: `hit`, `miss`, or `upload`.

Cache tier: `memory` or `cloud`.

Cache type: `action` for action cache, `cas` for content-addressable storage.

Executed action stage.

Process exit code of an executed action.

HTTP method: `GET`, `POST`, ...

HTTP response code: `200`, `302`, `401`, `404`, `500`, ...

HTTP route before substituting path parameters (`/invocation/:id`, `/settings`, ...).

Invocation status: `success`, `failure`, `disconnected`, or `unknown`.

Status of the database connection: `in_use` or `idle`.

SQL DB replica role: `primary` for read+write replicas, or `read_replica` for read-only DB replicas.

SQL query before substituting template parameters.

Status code as defined by [grpc/codes](https://godoc.org/google.golang.org/grpc/codes#Code).

Type of event sent to BuildBuddy's webhook handler: `push` or `pull_request`.