Convert REST API to Java

[steven-sheehy]

Problem
The current JavaScript REST API component is not properly layered, mixing HTTP, business logic and SQL construction all within the same layer. The SQL construction in particular is quite error prone and a maintenance burden. We'd also like to reuse code with other modules.

Solution
Convert the REST API to Spring WebFlux and JPA. Using the OpenAPI spec as a contract, generate the Spring WebFlux scaffolding and fill in the service and repository layers. As this is a large effort, we should do it one by one hiding the separate processes behind an API gateway so they appear as a unified API.

Alternatives
Properly layer current module into controller, service, domain and ORM-based repository layer.

Additional Context