feat: Start implementing roles (and domainless service users)

src/db/error.rs

@@ -5,12 +5,18 @@ use crate::db::UserRef;
 pub type BoxedError = Box<dyn std::error::Error + Send + Sync + 'static>;
 
 #[derive(Debug)]
-pub struct UserAlreadyExists(pub UserRef);
+pub enum UserCreationError {
+    UserAlreadyExists(UserRef),
+    Permissions,
+}
 
-impl fmt::Display for UserAlreadyExists {
+impl fmt::Display for UserCreationError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "User already exists: {}", self.0)
+        match self {
+            Self::UserAlreadyExists(user) => write!(f, "User already exists: {user}"),
+            Self::Permissions => write!(f, "You do not have permissions to create this user"),
+        }
     }
 }
 
-impl std::error::Error for UserAlreadyExists {}
+impl std::error::Error for UserCreationError {}