Improve docs for lazy loading

ruma-client-api/src/r0/filter.rs

@@ -93,6 +93,8 @@ pub struct RoomEventFilter<'a> {
     pub url_filter: Option<UrlFilter>,
 
     /// Options to control lazy-loading of membership events.
+    ///
+    /// Defaults to `LazyLoadOptions::Disabled`.
     #[serde(flatten)]
     pub lazy_load_options: LazyLoadOptions,
 }

ruma-client-api/src/r0/filter/lazy_load.rs

@@ -29,6 +29,13 @@ impl LazyLoadOptions {
     }
 }
 
+impl Default for LazyLoadOptions {
+    /// `LazyLoadOptions::Disabled`
+    fn default() -> Self {
+        Self::Disabled
+    }
+}
+
 impl Serialize for LazyLoadOptions {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -53,12 +60,6 @@ impl Serialize for LazyLoadOptions {
     }
 }
 
-impl Default for LazyLoadOptions {
-    fn default() -> Self {
-        Self::Disabled
-    }
-}
-
 struct LazyLoadOptionsVisitor;
 
 impl<'de> Visitor<'de> for LazyLoadOptionsVisitor {