refactor: move config defaults from TOML files to Default trait (#352)

crates/common_utils/src/ext_traits.rs

@@ -353,3 +353,34 @@ impl<A: Send, B> AsyncExt<A, B> for Option<A> {
         }
     }
 }
+
+/// Extension trait for validating application configuration. This trait provides utilities to
+/// check whether the value is either the default value or is empty.
+pub trait ConfigExt {
+    /// Returns whether the value of `self` is the default value for `Self`.
+    fn is_default(&self) -> bool
+    where
+        Self: Default + PartialEq<Self>,
+    {
+        *self == Self::default()
+    }
+
+    /// Returns whether the value of `self` is empty after trimming whitespace on both left and
+    /// right ends.
+    fn is_empty_after_trim(&self) -> bool;
+
+    /// Returns whether the value of `self` is the default value for `Self` or empty after trimming
+    /// whitespace on both left and right ends.
+    fn is_default_or_empty(&self) -> bool
+    where
+        Self: Default + PartialEq<Self>,
+    {
+        self.is_default() || self.is_empty_after_trim()
+    }
+}
+
+impl ConfigExt for String {
+    fn is_empty_after_trim(&self) -> bool {
+        self.trim().is_empty()
+    }
+}