Refactor mobile to use OpenApi generated SDK (#336)

mobile/openapi/lib/api_exception.dart

@@ -0,0 +1,33 @@
+//
+// AUTO-GENERATED FILE, DO NOT MODIFY!
+//
+// @dart=2.12
+
+// ignore_for_file: unused_element, unused_import
+// ignore_for_file: always_put_required_named_parameters_first
+// ignore_for_file: constant_identifier_names
+// ignore_for_file: lines_longer_than_80_chars
+
+part of openapi.api;
+
+class ApiException implements Exception {
+  ApiException(this.code, this.message);
+
+  ApiException.withInner(this.code, this.message, this.innerException, this.stackTrace);
+
+  int code = 0;
+  String? message;
+  Exception? innerException;
+  StackTrace? stackTrace;
+
+  @override
+  String toString() {
+    if (message == null) {
+      return 'ApiException';
+    }
+    if (innerException == null) {
+      return 'ApiException $code: $message';
+    }
+    return 'ApiException $code: $message (Inner exception: $innerException)\n\n$stackTrace';
+  }
+}