Add in production container build

[stephencshelton]

🎫 Ticket

Helm chart for deploying identity-idp

🛠 Summary of changes

Adds in the ability to build a RAILS_ENV=production image for use with a helm chart.

• Adds the ability to set application configuration through environment variables
• Adds in a docker-compose file to run the stack locally
• Adds the puma gem for running ssl in a container without having to use something like passenger
• Adds the ability to configure the database sslmode for use with ephemeral environments

👀 Screenshots

Currently running at https://test.review-app.identitysandbox.gov/

[mitchellhenke]

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