Document strfry integration

docs/dev/nostr.md

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+# Nostr
+
+## strfry
+
+The `extras/strfry` directory contains code to integrate [strfry][1] with
+akkounts, so that notes published to the relay have to be authored by (or in
+some cases just related to) local users who have verified their Nostr public
+key.
+
+### Requirements
+
+[Deno](https://deno.com/) needs to be installed on the machine that you run
+strfry on.
+
+We provide a Docker image with recent strfry and Deno builds:
+
+https://gitea.kosmos.org/kosmos/-/packages/container/strfry-deno/
+
+### Configuration
+
+You can use either environment variables (see e.g. the `strfry` service in
+`docker-compose-yml`) or a local `.env` file in the same working directory
+that you place the extra files in (e.g. `/opt/strfry`).
+
+In your `strfry.conf`, configure `strfry-policy.ts` as the write policy, like so:
+
+```
+writePolicy {
+    plugin = "/opt/strfry/strfry-policy.ts"
+}
+```
+
+All dependencies will be downloaded and cached automatically when the plugin is
+called for the first time.
+
+### Manual tasks
+
+You can sync all notes authored by local users (any account that has verified
+their Nostr pubkey with akkounts) from a remote [strfry][1] relay via negentropy
+sync:
+
+    deno run -A /opt/strfry/strfry-sync.ts wss://nostr.kosmos.org
+
+Or, in the running container when using Docker Compose:
+
+    docker compose exec strfry deno run -A /opt/strfry/strfry-sync.ts wss://nostr.kosmos.org
+
+The `strfry` service container also exposes the local relay on your local host
+on port 4777.
+
+[nak](https://github.com/fiatjaf/nak) is a helpful tool for manual Nostr tasks.
+Here's how you can grab a note by its event ID from a remote relay and publish
+it to your local strfry for example:
+
+    nak req -i 0fb010192685b86b0810b3de3706fbbf3b8c1db30b14533094a2b9700c820cdc nostr.kosmos.org | nak event ws://localhost:4777
+
+[1]: https://github.com/hoytech/strfry