Refactor API Schema and validation

- /schema now returns full openapi/swagger schema
- That schema is used to validate incoming requests
- And used as a contract in future integration tests
- Moved route files up one level
- Fixed incorrect 404 reponses when getting objects
- Fixed saving new objects and passing jsonschemavalidation

backend/schema/paths/schema/get.json

@@ -0,0 +1,10 @@
+{
+	"operationId": "schema",
+	"summary": "Returns this swagger API schema",
+	"tags": ["Public"],
+	"responses": {
+		"200": {
+			"description": "200 response"
+		}
+	}
+}