Revert "Remove unused Loggable::extended_arrow_datatype (#7260)"

This reverts commit 0252f6b.

crates/store/re_types_core/src/loggable.rs

@@ -1,3 +1,5 @@
+use std::sync::Arc;
+
 use crate::{
     result::_Backtrace, DeserializationResult, ResultExt as _, SerializationResult, SizeBytes,
 };
@@ -39,6 +41,21 @@ pub trait Loggable: 'static + Send + Sync + Clone + Sized + SizeBytes {
     where
         Self: 'a;
 
+    // --- Optional metadata methods ---
+
+    /// The underlying [`arrow2::datatypes::DataType`], including datatype extensions.
+    ///
+    /// The default implementation will simply wrap [`Self::arrow_datatype`] in an extension called
+    /// [`Self::name`], which is what you want in most cases.
+    #[inline]
+    fn extended_arrow_datatype() -> arrow2::datatypes::DataType {
+        arrow2::datatypes::DataType::Extension(
+            Self::name().to_string(),
+            Arc::new(Self::arrow_datatype()),
+            None,
+        )
+    }
+
     // --- Optional serialization methods ---
 
     /// Given an iterator of owned or reference values to the current [`Loggable`], serializes

crates/store/re_types_core/src/tuid.rs

@@ -64,14 +64,8 @@ impl Loggable for Tuid {
         ];
         let validity = None;
 
-        let datatype = arrow2::datatypes::DataType::Extension(
-            Self::name().to_string(),
-            Arc::new(Self::arrow_datatype()),
-            None,
-        );
-
         // TODO(cmc): We use the extended type here because we rely on it for formatting.
-        Ok(StructArray::new(datatype, values, validity).boxed())
+        Ok(StructArray::new(Self::extended_arrow_datatype(), values, validity).boxed())
     }
 
     fn from_arrow(array: &dyn ::arrow2::array::Array) -> crate::DeserializationResult<Vec<Self>> {