Architecture decisions

These records describe the architecture of pulse-cli as it is today, as a set of decisions: what was decided, what follows from it, and which alternatives were turned down and why. They are not a history. When a decision changes, its record is edited in place so that it stays true.

Change a record in the same pull request that changes what it describes. Every record has the same sections: Context, Decision, Consequences, Rejected alternatives.

1. Engines as adapters, the API as its own folder: one adapter per engine behind one port, shared code per API.
2. Camunda 8 is a separate API: why Camunda 8 would be a new API with its own adapter, not a fourth engine of the Camunda 7 REST API.