add an API key definition within the OpenAPI spec

Author: sergejsvisockis

api/src/main/resources/document-service-api-v1.yaml

@@ -194,3 +194,12 @@ components:
           type: string
         fileName:
           type: string
+  securitySchemes:
+    ApiKeyAuth:
+      type: apiKey
+      in: header
+      name: x-api-key
+      description: An authentication API key
+
+security:
+  - ApiKeyAuth: [ ]