How-To: Write and Enable a Nexus Delta Plugin

Use cases to cover:

- managing resources
- routes
- packaging

What plugin should we do?

- [ ] Expose counts (type of resources) through the API
- [ ] Projections in Neo4j (property-graphs support in Nexus) (preferred, only if we end up developing this feature)
- [x] Archive (does not index anything)

Acceptance Criteria:

- explain the goal of the plugin
- step by step changes (code) and reasoning to get to this goal
- reference to the actual archive plugin
- shortcomings (indexing not covered with the archive plugin)
- packaging and deployment (need separate git repo)

Start by locating the actual archive plugin and the Nexus plugin packaging and deployment entry points. Use them to document the plugin goal, step-by-step code changes and reasoning, resource management, routes, packaging, and the archive plugin's indexing limitation. Done means the guide covers deployment from a separate Git repository and all listed acceptance criteria.

Written by the indexing model from the issue text.