feat(IPCEICIS-1835): 👽 Added api specification as local file

backstage wanted me the explicitly example.com to look up the api specification. Since this is just a dummy example, I generated an api spec myself and put it here

api-spec.yaml

@@ -0,0 +1,42 @@
+openapi: 3.0.0
+info:
+  title: Example API
+  description: Eine einfache API für Demonstrationszwecke
+  version: 1.0.0
+servers:
+  - url: https://api.example.com/v1
+paths:
+  /users:
+    get:
+      summary: Liste aller Benutzer
+      responses:
+        '200':
+          description: Erfolgreiche Antwort
+          content:
+            application/json:    
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/User'
+    post:
+      summary: Erstelle einen neuen Benutzer
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/User'
+      responses:
+        '201':
+          description: Benutzer erfolgreich erstellt
+components:
+  schemas:
+    User:
+      type: object
+      properties:
+        id:
+          type: integer
+        name:
+          type: string
+        email:
+          type: string

catalog-entity.yaml

@@ -8,4 +8,4 @@ spec:
   lifecycle: production
   owner: team-api
   definition:
-    $text: https://example.com/api-spec.yaml
+    $text: ./api-spec.yaml