Remove requirement that deprecated property 'target' is provided

The target property has been deprecated for a long time on an EntityRelation, but
is still required in the spec. This fix removes that requirement, but keeps it
around for now.

Signed-off-by: Rickard Dybeck <dybeck@spotify.com>

.changeset/rich-owls-smell.md

@@ -0,0 +1,5 @@
+---
+'@backstage/catalog-model': patch
+---
+
+Remove requirement for 'target' property of EntityRelation

packages/catalog-model/src/schema/shared/common.schema.json

@@ -32,7 +32,7 @@
       "$id": "#relation",
       "type": "object",
       "description": "A directed relation from one entity to another.",
-      "required": ["type", "target", "targetRef"],
+      "required": ["type", "targetRef"],
       "additionalProperties": false,
       "properties": {
         "type": {

packages/catalog-model/src/validation/entitySchemaValidator.test.ts

@@ -365,11 +365,6 @@ describe('entitySchemaValidator', () => {
     expect(() => validator(entity)).toThrow(/relations/);
   });
 
-  it('does reject missing relations.target', () => {
-    delete entity.relations[0].target;
-    expect(() => validator(entity)).toThrow(/relations/);
-  });
-
   it('does reject missing relations.targetRef', () => {
     delete entity.relations[0].targetRef;
     expect(() => validator(entity)).toThrow(/relations/);