`export_local` creates file with double file extension

### Bug Summary

When `filename` is specified, it appends `.json` regardless if the file already has the extension

### Reproduction Repository (if applicable)

_No response_

### Steps to Reproduce

Call `export_local` with a `filename` such as `test.json` and it will produce a file called `test.json.json`.

```
req()
.send({
operation: 'export_local',
path: './',
filename: 'test.json',
format: 'json'
});
```

### Expected Behavior

Should only append the format file extension if the `filename` doesn't have the extension already.

### Actual Behavior

Export will create a file with double extension (e.g. `test.json.json`).

### Platform

Harper 5 (main branch)

### Console Errors

_No response_

### Screenshots or Videos

_No response_

### Additional Context

This issue was found while running integration tests, namely `7_jobsAndJobRoleTesting.mjs`.

### Are you planning to fix this issue?

No, just reporting the issue

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