Add Sentry integration

[yammesicka]

• Add Sentry machine to our Dockerfile.
• Add some logs to the project.
• Use the Flask integration plugin of Sentry.
• Use the Celery integration plugin of Sentry.
• Ensure proper integration and allow admins to login Sentry and view logs.

See also: Flask documentation about Sentry.

[jungrishi]

@yammesicka can I work on this?

[yammesicka]

Yeah, sure :)