Add toy implementation of association rollup

xmtp_id/Cargo.toml

@@ -19,3 +19,5 @@ prost.workspace = true
 tls_codec.workspace = true
 chrono.workspace = true
 serde.workspace = true
+sha2 = "0.10.8"
+rand.workspace = true

xmtp_id/src/associations/entity.rs

@@ -0,0 +1,42 @@
+#[derive(Clone, Debug, PartialEq)]
+pub enum EntityRole {
+    Installation,
+    Address,
+    LegacyKey,
+}
+
+#[derive(Clone, Debug)]
+pub struct Entity {
+    pub role: EntityRole,
+    pub id: String,
+    pub is_revoked: bool,
+}
+
+impl Entity {
+    pub fn new(role: EntityRole, id: String, is_revoked: bool) -> Self {
+        Self {
+            role,
+            id,
+            is_revoked,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::associations::test_utils;
+
+    use super::*;
+
+    use test_utils::rand_string;
+
+    impl Default for Entity {
+        fn default() -> Self {
+            Self {
+                role: EntityRole::Address,
+                id: rand_string(),
+                is_revoked: false,
+            }
+        }
+    }
+}