feat(backend): Phase 2.5 permission and share models

backend/src/models/permission.rs

@@ -0,0 +1,33 @@
+use serde::{Deserialize, Serialize};
+use strum::{Display, EnumString};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, Display, EnumString)]
+#[serde(rename_all = "lowercase")]
+#[strum(serialize_all = "lowercase")]
+pub enum Permission {
+    Read,
+    Write,
+    Delete,
+    Share,
+    Admin,
+}
+
+impl Permission {
+    pub fn can_read(&self) -> bool {
+        matches!(self, Self::Read | Self::Admin)
+    }
+    
+    pub fn can_write(&self) -> bool {
+        matches!(self, Self::Write | Self::Admin)
+    }
+    
+    pub fn can_delete(&self) -> bool {
+        matches!(self, Self::Delete | Self::Admin)
+    }
+    
+    pub fn can_share(&self) -> bool {
+        matches!(self, Self::Share | Self::Admin)
+    }
+}
+
+pub type Permissions = Vec<Permission>;