Add artifact provenance and stage skip outcomes

internal/artifactmodel/metadata.go

@@ -0,0 +1,17 @@
+package artifactmodel
+
+// ContractMetadata identifies the data contract implemented by an artifact.
+type ContractMetadata struct {
+	MediaType     string `json:"media_type"`
+	SchemaID      string `json:"schema_id"`
+	SchemaVersion string `json:"schema_version"`
+	ModuleKey     string `json:"module_key,omitempty"`
+}
+
+// ExternalProvenance identifies an artifact produced by an external system.
+type ExternalProvenance struct {
+	System     string `json:"system"`
+	RunID      string `json:"run_id"`
+	PipelineID string `json:"pipeline_id"`
+	ArtifactID string `json:"artifact_id"`
+}