As part of #574, we want to offer users a standalone proof-of-concept RPC service to serve as an example of a data companion. To this end, we want an ADR that captures:

1. The overall architecture of our standalone RPC service (implemented as a data companion)
2. Which of our RPC endpoints we'll be exposing as /v1
3. The decision as to which database to use to facilitate (1). The best database here will depend on the data access patterns defined by (1).

Future efforts could possibly involve productionizing this to the point that it may be able to scale independently of a full node, possibly reducing the costs associated with providing an RPC as a service, but this work needs to be broken down in separate follow-up issues.