make multi-protocol identity feature

src/profile/identity/auth/memory/error.rs

@@ -0,0 +1,20 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Clear,
+    Overwrite(String),
+    Unexpected,
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Clear => write!(f, "Could not cleanup memory index"),
+            Self::Overwrite(key) => {
+                write!(f, "Overwrite attempt for existing record `{key}`")
+            }
+            Self::Unexpected => write!(f, "Unexpected error"),
+        }
+    }
+}