fix: preview show error stack trace

[devnamrits]

Closes #5907 #4070

Summary:
It will elaborately describe the error by showing the stack trace of the error.

As of now, only the error message is being shown in the UI which makes it difficult to debug things in the app.

Test plan

Checklist

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[devnamrits]

@erezrokah
I have raised draft PR. What's next?? Will it be merged??
Or, meanwhile, I've to wait?? If I've to wait then can I jump to other issues??

Please explain the further procedure. Sorry for being so silly.

[erezrokah]

Thanks @devnamrits, give me some time to test this.

You can look at other issues if you'd like

[devnamrits]

@erezrokah
Thank you for your kind response. Meanwhile, I'm looking into other issues.

[erezrokah]

@devnamrits, looks like some CI tests are failing, can you look into it?
You can those via yarn test. See https://github.com/netlify/netlify-cms/blob/964d6975dff599dd9afa55deae9c54a6630c0d96/CONTRIBUTING.md#test

[devnamrits]

@erezrokah Looking into this.

[devnamrits]

@erezrokah Created a new state variable named as errorTitle because while creating the issue URL we're using just errorMessage rather than using the whole error stack. Also since we're generating snapshots for tests we run. In the case of ErrorBoundary.js, we're generating a snapshot of the error UI which will contain the error trace. So the snapshots will contain those error traces as well which will vary from user to user due to different local directory configurations. Hence, after updating test snapshots, all tests are passing.

[erezrokah]

Thanks for this @devnamrits, I removed the snapshot validation as it does more harm than good in this case.
I also added some logic to cleanup the stack trace, see