LSIF: Add endpoint to directly enqueue job.

Created by: efritz

This will help us debug in the future when we need to explicitly run a scheduled job in order to see it fail rather than wait for its next scheduled time in the future.

Will also be more useful in general if, for example, an admin wants to run a cleanup job immediately rather than wait 8 hours for the next cleanup routine.

In the future this will be exposed in a more direct way (via GraphQL API with the rest of the jobs/dumps endpoints). For now, it should be accessed only in dev or from within the container via curl for quick-and-easy debugging.