[Auth] Restore User decoding to pre-11 behavior

[ncooke3]

The logging out was happening because the User.init(coder:) implementation in Firebase 11 was returning nil for cases where it previously hadn't in previous major versions.

Firebase 11 returned nil when any of the following was nil:

firebase-ios-sdk/FirebaseAuth/Sources/Swift/User/User.swift

Lines 1706 to 1715 in 4e5fbe8

	guard let userID = coder.decodeObject(of: NSString.self, forKey: kUserIDCodingKey) as? String,
	let apiKey = coder.decodeObject(of: NSString.self, forKey: kAPIKeyCodingKey) as? String,
	let appID = coder.decodeObject(
	of: NSString.self,
	forKey: kFirebaseAppIDCodingKey
	) as? String,
	let tokenService = coder.decodeObject(of: SecureTokenService.self,
	forKey: kTokenServiceCodingKey) else {
	return nil
	}

But Firebase 10.29.0 returned nil in only 2 cases:

firebase-ios-sdk/FirebaseAuth/Sources/User/FIRUser.m

Lines 360 to 362 in eca84fd

	if (!userID || !tokenService) {
	return nil;
	}

PR #9046 started encoding an app ID key to the user's archived format and that was first released in 8.11.0, so when updating from < 8.11 to 11+, the user instance would fail decoding with the early exit since the app ID couldn't be unarchived.

This failed silently through Firebase 10 because the Objective-C impl. didn't early exit and a nil decoding was silently allowed.

Testing:

1. Auth QS with 8.8 -> sign in with a user
2. Auth QS with 11.4 -> confirmed user is logged out
3. Auth QS with 11.4 with this fix -> confirmed user logs in at app startup

Fixes #14011

#no-changelog

[paulb777]

Great find! I'll merge to get it into the nightlies.

[JCsplash]

@paulb777 Thanks for merging! How long does it take for this fix to get into a stable release? Should we wait until 11.5.0 is officially released to update our pod?

[paulb777]

We'll sort out the release plan for the fix early next week.

It's up to you if you want to wait for the release or patch the fix into your current build.