Support provisioning of serverless services where possible

[tomaszchabinka]

Is your feature request related to a problem? Please describe.
README contains following statement:
the collection of resources created by these scripts will generate AWS costs of around $0.41 USD per hour ($10.00 USD per day) while the platform is in a mostly-idle pre-production state. This cost will grow proportionally to your production work loads.

I think this is a lot, especially for smaller/non-profit organizations. It seems that OpenEDX deployment shouldn't cost more than $50/month, as this is what some SaaS providers charge (e.g.: https://raccoongang.com/open-edx-services/tanuki/

Wondering if this costs could be reduced

Describe the solution you'd like
I think switching from server-dependant to serverless services could be a potential solutions. For example, Terraform could create:

• AWS RDS Aurora Serverless instead of AWS RDS MySQL
• MongoDB Atlas Serverless instead of MongoDB
• AWS ElastiCache Serverless instead of regular AWS ElastiCache

Describe alternatives you've considered
N/A

Additional context
N/A