fix(firestore): do not return idField on valueChanges if no document

[KingDarBoja]

Checklist

• Issue number for this PR: idField on valueChanges doesn't work as expected. #2753 (required)
• Docs included?: no
• Test units included?: yes
• In a clean directory, yarn install, yarn test run successfully? no (needs some fix for Windows)

Description

This should provide a safe way of returning the idField on document method valueChanges as the current behaviour is explained at the linked issue. In this case, the idField should only ever be returned if the document exists.

Code sample

[KingDarBoja]

I have no idea why the test isn't working when it does locally on my machine 🤔

[davideast]

Hey @KingDarBoja! We really do appreciate the PR but this would constitute a breaking change if we merged it into the main codebase. We are working on a new version of the library (#2770) and we could add it in there in the future, but right now we need to keep the library stable until then.

Would you be interested in adding this change in the near future when we are ready to accept PRs against the new lib version? I'll ping you in this thread to let you know when we are ready.

[KingDarBoja]

No worries! Feel free to ping me when you guys ready, I am also around at the Angular Discord server in any case I forgot to check this PR 😄

[jamesdaniels]

This should now be addressed in rxfire/firestore#doc and @angular/fire/firestore#docValue, we opted to avoid breaks in @angular/fire/compat/firestore as I consider that (largely) feature complete.