feat(log): add bounded diagnostic transport

libs/kaptan-log-derive/tests/ui.rs

@@ -0,0 +1,7 @@
+#[test]
+fn kaptan_error_expands_for_enum_shapes_only() {
+    let tests = trybuild::TestCases::new();
+    tests.pass("tests/ui/enum.rs");
+    tests.compile_fail("tests/ui/struct.rs");
+    tests.compile_fail("tests/ui/union.rs");
+}