Make it clearer that only node-API should be listed in `local_nodes.json`

[surchs]

Description

@barbarastrasser mentioned that from the docs it was not clear enough that local_nodes.json should only contain the addresses of node-APIs, and not any federation-APIs.

If you get this wrong, bad things will happen: https://github.com/neurobagel/federation-api/issues/89

Relevant documentation pages

No response

Additional details

No response

[github-actions[bot]]

We want to keep our issues up to date and active. This issue hasn't seen any activity in the last 75 days. We have applied the _flag:stale label to indicate that this issue should be reviewed again. When you review, please reread the spec and then apply one of these three options:

• prioritize: apply the flag:schedule label to suggest moving this issue into the backlog now
• close: if the issue is no longer relevant, explain why (give others a chance to reply) and then close.
• archive: sometimes an issue has important information or ideas but we won't work on it soon. In this case apply the someday label to show that this won't be prioritized. The stalebot will ignore issues with this label in the future. Use sparingly!