Allow a domain entity to have a domain so that a domain hierarchy can be represented.

Signed-off-by: Dawn James <dawnj@spotify.com>

packages/catalog-model/examples/all-domains.yaml

@@ -5,5 +5,6 @@ metadata:
   description: A collection of all Backstage example domains
 spec:
   targets:
+    - ./domains/audio-domain.yaml
     - ./domains/artists-domain.yaml
     - ./domains/playback-domain.yaml

packages/catalog-model/examples/domains/artists-domain.yaml

@@ -11,3 +11,4 @@ metadata:
       icon: dashboard
 spec:
   owner: team-a
+  domain: audio

packages/catalog-model/examples/domains/audio-domain.yaml

@@ -0,0 +1,13 @@
+apiVersion: backstage.io/v1alpha1
+kind: Domain
+metadata:
+  name: audio
+  description: Everything related to audio
+  links:
+    - url: http://example.com/domain/audio/
+      title: Domain Readme
+    - url: http://example.com/domains/audio/dashboard
+      title: Domain Metrics Dashboard
+      icon: dashboard
+spec:
+  owner: acme-corp

packages/catalog-model/src/kinds/DomainEntityV1alpha1.test.ts

@@ -31,6 +31,7 @@ describe('DomainV1alpha1Validator', () => {
       },
       spec: {
         owner: 'me',
+        domain: 'parent',
       },
     };
   });
@@ -68,4 +69,19 @@ describe('DomainV1alpha1Validator', () => {
     (entity as any).spec.owner = '';
     await expect(validator.check(entity)).rejects.toThrow(/owner/);
   });
+
+  it('accepts missing domain', async () => {
+    delete (entity as any).spec.domain;
+    await expect(validator.check(entity)).resolves.toBe(true);
+  });
+
+  it('rejects wrong domain', async () => {
+    (entity as any).spec.domain = 7;
+    await expect(validator.check(entity)).rejects.toThrow(/domain/);
+  });
+
+  it('rejects empty domain', async () => {
+    (entity as any).spec.domain = '';
+    await expect(validator.check(entity)).rejects.toThrow(/domain/);
+  });
 });

packages/catalog-model/src/kinds/DomainEntityV1alpha1.ts

@@ -32,6 +32,7 @@ export interface DomainEntityV1alpha1 extends Entity {
   kind: 'Domain';
   spec: {
     owner: string;
+    domain?: string;
   };
 }
 

packages/catalog-model/src/schema/kinds/Domain.v1alpha1.schema.json

@@ -11,7 +11,8 @@
         "description": "Everything about artists"
       },
       "spec": {
-        "owner": "artist-relations-team"
+        "owner": "artist-relations-team",
+        "domain": "artists"
       }
     }
   ],
@@ -38,6 +39,12 @@
               "description": "An entity reference to the owner of the component.",
               "examples": ["artist-relations-team", "user:john.johnson"],
               "minLength": 1
+            },
+            "domain": {
+              "type": "string",
+              "description": "An entity reference to the domain that the system belongs to.",
+              "examples": ["artists"],
+              "minLength": 1
             }
           }
         }