Add entity status structs (#50)

Backstage _may_ export information on entity Status, this PR adds
support for that.

backstage/entity.go

@@ -26,6 +26,9 @@ type Entity struct {
 
 	// Relations that this entity has with other entities.
 	Relations []EntityRelation `json:"relations,omitempty"`
+
+	// The current status of the entity, as claimed by various sources.
+	Status *EntityStatus `json:"status,omitempty"`
 }
 
 // EntityMeta represents metadata fields common to all versions/kinds of entity.
@@ -108,6 +111,46 @@ type EntityRelationTarget struct {
 	Namespace string `json:"namespace"`
 }
 
+// EntityStatus informs current status of the entity, as claimed by various sources.
+// https://github.com/backstage/backstage/blob/master/packages/catalog-model/src/schema/shared/common.schema.json
+type EntityStatus struct {
+	// A specific status item on a well known format.
+	Items []EntityStatusItem `json:"items,omitempty"`
+}
+
+// EntityStatusItem contains a specific status item on a well known format.
+// https://github.com/backstage/backstage/blob/master/packages/catalog-model/src/schema/shared/common.schema.json
+type EntityStatusItem struct {
+	// The item type
+	Type string `json:"type"`
+
+	// The status level / severity of the status item.
+	// Either ["info", "warning", "error"]
+	Level string `json:"level"`
+
+	// A brief message describing the status, intended for human consumption.
+	Message string `json:"message"`
+
+	// An optional serialized error object related to the status.
+	Error *EntityStatusItemError `json:"error"`
+}
+
+// EntityStatusItemError has aA serialized error object.
+// https://github.com/backstage/backstage/blob/master/packages/catalog-model/src/schema/shared/common.schema.json
+type EntityStatusItemError struct {
+	// The type name of the error"
+	Name string `json:"name"`
+
+	// The message of the error
+	Message string `json:"message"`
+
+	// An error code associated with the error
+	Code *string `json:"code"`
+
+	// An error stack trace
+	Stack *string `json:"stack"`
+}
+
 // ListEntityOrder defines a condition that can be used to order entities.
 type ListEntityOrder struct {
 	// Direction is the direction to order by.

backstage/testdata/entities.json

@@ -421,5 +421,44 @@
     "relations":[
 
     ]
+  },
+  {
+    "metadata":{
+      "namespace":"default",
+      "annotations":{
+        "backstage.io/managed-by-location":"file:/private/tmp/back/examples/org.yaml",
+        "backstage.io/managed-by-origin-location":"file:/private/tmp/back/examples/org.yaml"
+      },
+      "name":"generated-aa156660b91ff3cfa0819c08e413581e6d4e4136",
+      "uid":"f5e4edef-f547-430d-8fee-13f4919888b7",
+      "etag":"d9b5d5f05fe7901d90c68b62a9b2d30b3f9f0f87"
+    },
+    "apiVersion":"backstage.io/v1alpha1",
+    "kind":"Location",
+    "spec":{
+      "type":"file",
+      "target":"/private/tmp/back/examples/org.yaml"
+    },
+    "relations":[
+
+    ],
+    "status": {
+      "items": [
+        {
+          "type": "backstage.io/catalog-processing",
+          "level": "error",
+          "message": "SomeError: it broke",
+          "error": {
+            "name": "SomeError",
+            "message": "Error message",
+            "cause": {
+              "name": "Error",
+              "message": "error message",
+              "stack": "stack trace"
+            }
+          }
+        }
+      ]
+    }
   }
 ]