enhancement: timestamps createdAt property immutable by default

[IslandRhythms]

So there is a failing test, however I'm not sure If the test needs to be fixed or my solution needs to be changed. The test is gh-9105

[AbdelrahmanHafez]

I'd say that such change is a breaking change and should not be included in a minor/patch release.
I think it's fine to set createdAt to be immutable by default, but if we choose to go that way, we need to move it to v6.0.

Also, would be neat to offer a global option to set createdAt to false for those who choose to.

[vkarpov15]

@AbdelrahmanHafez you're right about this being potentially backwards breaking, I'll merge this into 6.0 just to be safe.

Any ideas for syntax re: setting createdAt to false globally? Maybe mongoose.set('timestamps.createdAt', false)?

[AbdelrahmanHafez]

@vkarpov15
I'd go for mongoose.set('timestamps.createdAt.immutable', false), otherwise it can mislead people to think that this option sets timestamps to not add a createdAt field.

[vkarpov15]

@AbdelrahmanHafez would having an immutable createdAt break your code?

[AbdelrahmanHafez]

@vkarpov15
No, but I am anticipating that someone out there is updating the value of createdAt, and it would really make their lives difficult.

We can ship this as an option to set immutable globally on createdAt, to be false by default in v5, then change it to true by default in v6.