build(deps): bump mongoose from 7.2.1 to 8.1.3 in /apps/OpenSignServer

Bumps [mongoose](https://github.com/Automattic/mongoose) from 7.2.1 to 8.1.3.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Automattic/mongoose/compare/7.2.1...8.1.3)

---
updated-dependencies:
- dependency-name: mongoose
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

apps/OpenSignServer/package.json

@@ -29,7 +29,7 @@
     "generate-api-key": "^1.0.2",
     "jsonschema": "^1.4.1",
     "mailgun.js": "^9.3.0",
-    "mongoose": "^7.2.1",
+    "mongoose": "^8.1.3",
     "multer": "^1.4.5-lts.1",
     "multer-s3": "^2.10.0",
     "node-forge": "^1.3.1",