swarm-controller: make an existing forge user a site admin

POST /api/forge/users/{name}/admin reads the account and, when it is not
already a site admin, sets `admin` with admin_edit_user. It never
creates one: a human's account is made by their first authelia login,
so a missing one answers 404, saying the user has not logged in via SSO
yet. An existing admin is a success with nothing sent.

The edit carries `admin` alone. repo_creation_lockdown's login_name +
source_id = 0 would turn an SSO-made account into a local one: in
Forgejo 16 a source_id sets the login type.

An agent's name is refused, and so is any name when the roster can't be
read: a site admin ignores max_repo_creation, the lockdown that keeps an
agent's token from creating a repo and self-merging in it.

Refs #3782

swarm-controller/src/forge.rs

@@ -34,6 +34,7 @@ use utoipa::ToSchema;
 use crate::webhook::DeliveryKind;
 
 pub mod agent_token;
+pub mod site_admin;
 
 /// An agent's open config-PR, as [`Client::list_open_config_prs`] reports it
 /// and `GET /api/agents/{name}/config-pr` serves it.
@@ -1659,4 +1660,78 @@ mod tests {
         let body = lockdown_patch(&seen, "alice").expect("no lockdown PATCH sent");
         assert_eq!(body["max_repo_creation"], 0);
     }
+
+    /// Every `PATCH` body the stub saw.
+    fn patches(seen: &Seen) -> Vec<serde_json::Value> {
+        seen.lock()
+            .unwrap()
+            .iter()
+            .filter(|(method, _, _)| method == "PATCH")
+            .map(|(_, _, body)| body.clone())
+            .collect()
+    }
+
+    /// Only `admin` goes out: a `source_id` would reset an SSO-made
+    /// account's login type, and the other fields would overwrite the user's
+    /// own settings.
+    #[tokio::test]
+    async fn make_site_admin_sets_admin_and_nothing_else() {
+        let (client, seen) = stub_forge(
+            (404, "{}"),
+            (200, r#"{"login":"mara","is_admin":false}"#),
+            (200, "{}"),
+        )
+        .await;
+
+        let plan = client.make_site_admin("mara").await.unwrap();
+
+        assert_eq!(plan, site_admin::Plan::Promote);
+        let bodies = patches(&seen);
+        assert_eq!(bodies.len(), 1, "{bodies:?}");
+        let set: Vec<(&String, &serde_json::Value)> = bodies[0]
+            .as_object()
+            .unwrap()
+            .iter()
+            .filter(|(_, v)| !v.is_null())
+            .collect();
+        assert_eq!(set, [(&"admin".to_owned(), &serde_json::Value::Bool(true))]);
+    }
+
+    #[tokio::test]
+    async fn make_site_admin_leaves_an_admin_alone() {
+        let (client, seen) = stub_forge(
+            (404, "{}"),
+            (200, r#"{"login":"mara","is_admin":true}"#),
+            (200, "{}"),
+        )
+        .await;
+
+        let plan = client.make_site_admin("mara").await.unwrap();
+
+        assert_eq!(plan, site_admin::Plan::AlreadyAdmin);
+        assert!(patches(&seen).is_empty());
+    }
+
+    /// A user who has not logged in yet is reported, not created: nothing is
+    /// sent but the read.
+    #[tokio::test]
+    async fn make_site_admin_does_not_create_a_missing_user() {
+        let (client, seen) = stub_forge(
+            (201, "{}"),
+            (404, r#"{"message":"user does not exist"}"#),
+            (200, "{}"),
+        )
+        .await;
+
+        let plan = client.make_site_admin("mara").await.unwrap();
+
+        assert_eq!(plan, site_admin::Plan::NoSuchUser);
+        let methods: Vec<String> = seen
+            .lock()
+            .unwrap()
+            .iter()
+            .map(|(m, _, _)| m.clone())
+            .collect();
+        assert_eq!(methods, ["GET"]);
+    }
 }