add: block list stacks

crates/core/src/model/stacks.rs

@@ -23,6 +23,11 @@ pub enum StackMode {
     /// `users` vec contains ID of users to EXCLUDE from the timeline;
     /// every other user is included
     Exclude,
+    /// `users` vec contains ID of users to show in a user listing on the stack's
+    /// page (instead of a timeline).
+    ///
+    /// Other users can block the entire list (creating a `StackBlock`, not a `UserBlock`).
+    BlockList,
 }
 
 impl Default for StackMode {
@@ -70,3 +75,23 @@ impl UserStack {
         }
     }
 }
+
+#[derive(Serialize, Deserialize)]
+pub struct StackBlock {
+    pub id: usize,
+    pub created: usize,
+    pub initiator: usize,
+    pub stack: usize,
+}
+
+impl StackBlock {
+    /// Create a new [`StackBlock`].
+    pub fn new(initiator: usize, stack: usize) -> Self {
+        Self {
+            id: Snowflake::new().to_string().parse::<usize>().unwrap(),
+            created: unix_epoch_timestamp(),
+            initiator,
+            stack,
+        }
+    }
+}