add activity sequence

docs/unsure-where-to-put/star_activity.md

@@ -0,0 +1,22 @@
+```mermaid
+sequenceDiagram
+    participant fs as foreign_repository_server
+    participant os as our_repository_server
+
+    fs ->> os: post /api/activitypub/repository-id/1/inbox {Start-Activity}
+    activate os
+    os ->> os: validate request inputs
+    activate repository
+    os ->> repository: validate
+    repository ->> repository: search for reop with object-id
+    deactivate repository
+    activate person
+    os ->> person: validate
+    person ->> person: search for ser with actor-id
+    person ->> fs: get /api/activitypub/user-id/{id from actor}
+    person ->> person: create user from response
+    deactivate person
+    os ->> repository: execute star action
+    os -->> fs: 200 ok
+    deactivate os
+```