domain: add Processing entities and ports (Job, JobBatch, Plugin, Pipeline)

crates/domain/tests/entities/processing_pipeline.rs

@@ -0,0 +1,17 @@
+use domain::entities::ProcessingPipeline;
+use domain::value_objects::{StructuredData, SystemId};
+
+#[test]
+fn steps_ordered() {
+    let mut pipeline = ProcessingPipeline::new("asset.created");
+    assert!(pipeline.steps.is_empty());
+
+    pipeline.add_step(SystemId::new(), StructuredData::new());
+    pipeline.add_step(SystemId::new(), StructuredData::new());
+    pipeline.add_step(SystemId::new(), StructuredData::new());
+
+    assert_eq!(pipeline.steps.len(), 3);
+    assert_eq!(pipeline.steps[0].step_order, 0);
+    assert_eq!(pipeline.steps[1].step_order, 1);
+    assert_eq!(pipeline.steps[2].step_order, 2);
+}