Create backend spec

backend/spec/infra.md

@@ -0,0 +1,24 @@
+# `pub struct Infra`
+
+Infra is a service which polls the database and synchronizes updates to relays to a remote zooid instance via `api_url`.
+
+Members:
+
+- `api_url: String` - the URL of the zooid instance to be managed, from `ZOOID_API_URL`
+- `repo: Repo`
+
+## `pub fn new(repo: Repo) -> Self`
+
+- Reads environment and populates members
+
+## `pub async fn start(self)`
+
+Calls `self.tick` in a loop every 10 seconds.
+
+## `pub async fn tick(self)`
+
+Iterates over `repo.list_activity` since last run and does the following:
+
+- For any `relay_created|relay_updated` activity, sync relay config to zooid.
+- For any `relay_deactivated` activity, sync relay config to zooid.
+- If unsuccessful, call `repo.fail_relay_sync`.