BREAKING CHANGE: Fields in the internal scope of Parse Server (prefixed with underscore `_`) are only returned using the new `maintenanceKey`; previously the `masterKey` allowed reading of internal fields; see [access scopes](https://github.com/parse-community/parse-server#access-scopes) for a comparison of the keys' access permissions (#8212)
BREAKING CHANGE: The MongoDB aggregation pipeline requires native MongoDB syntax instead of the custom Parse Server syntax; for example pipeline stage names require a leading dollar sign like `$match` and the MongoDB document ID is referenced using `_id` instead of `objectId` (#8362)
BREAKING CHANGE: The mechanism to determine the client IP address has been rewritten; to correctly determine the IP address it is now required to set the Parse Server option `trustProxy` accordingly if Parse Server runs behind a proxy server, see the express framework's [trust proxy](https://expressjs.com/en/guide/behind-proxies.html) setting (#8372)
BREAKING CHANGE: The Node Package Manager lock file `package-lock.json` is upgraded to version 2; while it is backwards with version 1 for the npm installer, consider this if you run any non-npm analysis tools that use the lock file (#8285)
BREAKING CHANGE: This release introduces the asynchronous initialization of Parse Server to prevent mounting Parse Server before being ready to receive request; it changes how Parse Server is imported, initialized and started; it also removes the callback `serverStartComplete`; see the [Parse Server 6 migration guide](https://github.com/parse-community/parse-server/blob/alpha/6.0.0.md) for more details (#8232)
BREAKING CHANGE: Nested objects are now properly stored in the database using JSON serialization; previously, due to a bug only top-level objects were serialized, but nested objects were saved as raw JSON; for example, a nested `Date` object was saved as a JSON object like `{ "__type": "Date", "iso": "2020-01-01T00:00:00.000Z" }` instead of its serialized representation `2020-01-01T00:00:00.000Z` (#8209)
BREAKING CHANGE: The Parse Server option `enforcePrivateUsers` is set to `true` by default; in previous releases this option defaults to `false`; this change improves the default security configuration of Parse Server (#8283)
BREAKING CHANGE: This release restricts the use of `masterKey` to localhost by default; if you are using Parse Dashboard on a different server to connect to Parse Server you need to add the IP address of the server that hosts Parse Dashboard to this option (#8281)
