Add a check on startup to ensure application is not using default key in live environments

[AetherUnbound]

Description

In #3422, we altered the Django secret key to use a more obvious shim value. @dhruvkb suggested:

We can also update settings.py to raise an error if it's unchanged.

To be specific, we should check to ensure that the value is not example_key in any ENVIRONMENT that's not local or development, and raise an appropriate error if it is.

[sarayourfriend]

This would be the exception to raise for an issue of this nature: https://docs.djangoproject.com/en/4.2/ref/exceptions/#improperlyconfigured

[firatbezir]

Can i give it a shot?

[sarayourfriend]

I've assiged it to you @firatbezir, go for it 🙂

[obulat]

To be specific, we should check to ensure that the value is not example_key in any ENVIRONMENT that's not local or development, and raise an appropriate error if it is.

How do you get the example_key for all environments in Django settings?

[sarayourfriend]

I think Madison meant example_key as a literal string, like "example_key" != actual_value? Can you confirm @AetherUnbound?

[AetherUnbound]

That's correct!