Migrate email dispatching system from AWS Lambda to Celery queue

[pziemkowski]

Description

Since we're introducing Celery to the stack it's a good idea to migrate email dispatching to Celery task to use Django as much as possible and reduce code duplications.

Related to #493

Describe the solution you'd like

I'd like renderEmail to be called from within Celery task instead of AWS Lambda.

It should still use node to run the script, with exactly the same implementation as previously, just different task runner.

Describe alternatives you've considered

No response

Additional context

No response

Validations

• Follow our Code of Conduct.
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.