domain: add Identity & Access entities (User, Role, Permission, Group)

crates/domain/src/entities/group.rs

@@ -0,0 +1,46 @@
+use std::collections::HashSet;
+use crate::errors::DomainError;
+use crate::value_objects::SystemId;
+
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct Group {
+    pub group_id: SystemId,
+    pub name: String,
+    pub owner_user_id: SystemId,
+    pub members: HashSet<SystemId>,
+}
+
+impl Group {
+    pub fn new(name: impl Into<String>, owner_user_id: SystemId) -> Self {
+        let mut members = HashSet::new();
+        members.insert(owner_user_id);
+        Self {
+            group_id: SystemId::new(),
+            name: name.into(),
+            owner_user_id,
+            members,
+        }
+    }
+
+    pub fn add_member(&mut self, user_id: SystemId) -> Result<(), DomainError> {
+        if self.members.contains(&user_id) {
+            return Err(DomainError::Conflict(format!("User {user_id} is already a member")));
+        }
+        self.members.insert(user_id);
+        Ok(())
+    }
+
+    pub fn remove_member(&mut self, user_id: SystemId) -> Result<(), DomainError> {
+        if user_id == self.owner_user_id {
+            return Err(DomainError::Validation("Cannot remove the group owner".to_string()));
+        }
+        if !self.members.remove(&user_id) {
+            return Err(DomainError::NotFound(format!("User {user_id} is not a member")));
+        }
+        Ok(())
+    }
+
+    pub fn is_member(&self, user_id: &SystemId) -> bool {
+        self.members.contains(user_id)
+    }
+}