Upgrading parse-server from version 5.2.1 to 9.0.0 is a major update that includes several significant breaking changes. This automated upgrade by Snyk resolves security vulnerabilities but is very likely to break your application without manual code changes.

Here are some critical breaking changes you need to address:

1. Node.js Version Requirement: parse-server v9.0.0 requires Node.js version >= 18.18.0. Your package.json currently specifies "node": ">=12.22.10 <19". You must update your runtime environment to a compatible Node.js version and update the engines field in package.json accordingly to prevent deployment failures or runtime errors.

2. Database Configuration: The databaseURI configuration option for MongoDB was removed in Parse Server v7.0.0. You must migrate to using databaseAdapter. Your current configuration in index.js uses databaseURI and will cause the server to fail on startup.

   You'll need to modify index.js to use the databaseAdapter. Here is an example:

   // In index.js
   const { MongoAdapter } = require('parse-server/lib/Adapters/Database/Mongo/MongoAdapter');
   
   const config = {
     databaseAdapter: new MongoAdapter({
       uri: databaseUri || 'mongodb://localhost:27017/dev',
     }),
     // ... other config
   };

3. Other Breaking Changes: There are many other breaking changes across versions 6, 7, 8, and 9. It is crucial to review the official migration guides for each major version to identify all potential issues and required updates. You can find the guide in the parse-server repository (MIGRATION_GUIDE.md).

Given the extent of these changes, please carefully test your application after making the necessary updates.