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/internal/user.js

@@ -194,7 +194,7 @@ const internalUser = {
 				return query.then(utils.omitRow(omissions()));
 			})
 			.then((row) => {
-				if (!row) {
+				if (!row || !row.id) {
 					throw new error.ItemNotFoundError(data.id);
 				}
 				// Custom omissions