Implement Mongo Seeder

What does this MR do?

Adds a Mongo Seeder service.

• Populates User and Question DB if needed and shuts down.

Testing

• Ensure Docker's MongoDB instances have no documents in Users and Questions DBs.
• Run docker compose up --build.
• Login as with username 'a' and password 'a'.
• Question appears on page.

Relevant issues

Fixes missing seeding.