Add test for extra field

Signed-off-by: Christian Poveda <[email protected]>

Author: pvdrz

cyclonedx-bom-macros/tests/ui/pass/struct_with_extra_field.rs

@@ -0,0 +1,16 @@
+use cyclonedx_bom_macros::versioned;
+
+#[versioned("1.0", "2.0")]
+mod base {
+    pub struct Foo {
+        #[versioned("2.0")]
+        // This field only exists in version 2.0.
+        pub bar: u32,
+    }
+}
+
+fn main() {
+    // Version 1.0 does not have the `bar` field but 2.0 does.
+    let _old_foo = v1_0::Foo {};
+    let _new_foo = v2_0::Foo { bar: 0 };
+}