Needs estimate: make edge@lambda config storage more robust

[jsandoval81]

Stemming from a discussion with @jlkravitz about migrating environment config out of Lambda function code:

For standard Lambdas, the solution would be environment variables; however these are edge@Lambdas (distributed to the CDN edges) and AWS doesn't allow dynamic environment variables on those. Solutions like a JSON file or secrets service would require us to create a build step before function deployment. Where the config is either bundled with the function code (slower run-time perf) or injected as static code (faster run-time perf) before CDN distribution.

• (Backend) Update S3 upload bucket to have a deterministic domain
• (Backend) Update CDK pipeline for this Lambda to update / overwrite a JSON config file in the Lambda directory before deploying
• (Frontend) Update this Lambda to pull its domain config from a JSON file
• (Frontend) Update the frontend deployment pipeline values & coordinate GitHub secrets updates with Joshua

[isabeleliassen]

Turn into a ticket for an upcoming sprint. Likely to be a research + design solution type of task. Justin and John may meet to discuss options.