feat: nullable embedded entities

[andreamouraud]

Closes #3913

Description of change

This PR introduces a breaking change by modifying the embedded entities behaviour to make them nullable (maybe enable it under a specific config?)

When dealing with embedded entities where all columns are null, we can consider the entire entity to be null
The same principle applies when setting null as a value for the embedded entity while updating, it sets all the embedded columns to null

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run format to apply prettier formatting
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change
• The new commits follow conventions explained in CONTRIBUTING.md

[hinogi]

Exactly what .every is for 👍

[hinogi]

Suggested change

	(value) => value == null,
	(value) => value === null,

I guess you only want to check for null and not undefined?

[andreamouraud]

The unstrict check was intended, if we're getting an undefined value (it may not even be possible, didn't have a look at the underlying implementation) from the database it should still considered as a null in that use case

[hinogi]

In that case, I would make it explicit then.

Suggested change

	(value) => value == null,
	(value) => value === null || typeof value === 'undefined',

[andreamouraud]

would argue that this is the use case for unstrict equality 😄
had to rework it a bit for nested embedded entities in 73e4db3, added a comment to explicit it instead

[hinogi]

strict null check

[MatthieuVegreville]

would be great to merge this! is that planned in an upcoming release of typeORM?

[arieller]

Can this be merged?

[DevGJGlobal]

Hopefully this will be merged soon! 🥳

[pleerock]

I'll merge it despite it being a theoretical breaking change, because:

If you had such code in your codebase:

    @Column(() => NestedEmbedded)
    nested: NestedEmbedded | null
}

it couldn't work properly, because null cannot be skipped - it's not undefined.

The behavior under runtime value of null also was inappropriate, since it was not supported.

[pleerock]

Thank you for contribution! 🎉