errorMessage field in _PushStatus contains incorrect field

New Issue Checklist

• I am not disclosing a vulnerability.
• I am not just asking a question.
• I have searched through existing issues.
• I can reproduce the issue with the latest version of Parse Server.

Issue Description

The errorMessage field in the _PushStatus class contains a key different from most errors thrown on the server. For these particular cases, the SDKs may decode _PushStatus incorrectly.

Related to #7444

Steps to reproduce

Send a push notification that would produce an error so the errorMessage field is populated

Actual Outcome

The error message contains the key, message when most others would contain error.

["results": [["pushTime": "2022-06-08T01:39:28.694Z", "objectId": "LUYnqQCC4dQlCq70yVBPoELfJp8DazsC", "source": "rest", "numSent": 0, "errorMessage": ["code": 105, "message": "Invalid key name: _method"], "updatedAt": "2022-06-08T01:39:28.732Z", "createdAt": "2022-06-08T01:39:28.695Z", "query": "{\"_method\":\"GET\",\"limit\":100,\"skip\":0,\"where\":{\"objectId\":{\"$ne\":null}}}", "pushHash": "5064192be6a88ae013ae516b4601dc95", "ACL": [:], "status": "failed", "payload": "{\"alert\":{\"body\":\"Hello from ParseSwift!\"},\"badge\":1}"]]]

Expected Outcome

Error messages sent from the server are uniform always contain the same keys.

"errorMessage": ["code": 105, "error": "Invalid key name: _method"] // Most server errors contain "error" instead of message

Environment

Server

• Parse Server version: 5.2.0
• Operating system: Linux/docker
• Local or remote host (AWS, Azure, Google Cloud, Heroku, Digital Ocean, etc): local

Database

• System (MongoDB or Postgres): Postgres
• Database version: 14
• Local or remote host (MongoDB Atlas, mLab, AWS, Azure, Google Cloud, etc): local

Client

• SDK (iOS, Android, JavaScript, PHP, Unity, etc): Swift SDK
• SDK version: 4.5.0

Logs

The issue names the _PushStatus class but no file or test; start by tracing how its errorMessage field is assembled in Parse Server. Reproduce a failed push using the documented example and compare the returned key with the expected error key; done means the response is consistent with other server errors and the behavior is covered.