initial_snapshot: Accept unknown "emojiset" values

[MritunjayTiwari14]

Fixes #1981.

[chrisbobbe]

Let's make a new enum value unknown instead of using google.

[MritunjayTiwari14]

Thank you @chrisbobbe for the review, introduced a new enum value unknown to which all the unknow Emojiset are directed to.

[chrisbobbe]

Thanks! Small comments below.

[chrisbobbe]

nit: Emojiset.unknown

[chrisbobbe]

This .fromJson call will fail and need to be debugged each time we add a field to UserSettings.

Can you add a userSettings helper function in test/example_data.dart, on the pattern of similar helpers (like streamMessage or initialSnapshot), then I think this can just be

Suggested change

	final settings = UserSettings.fromJson({
	'twenty_four_hour_time': true,
	'display_emoji_reaction_users': true,
	'emojiset': unknownValue,
	'presence_enabled': true,
	});
	final json = eg.userSettings().toJson()..['emojiset'] = unknownValue;
	final settings = UserSettings.fromJson(json);

[MritunjayTiwari14]

Thank you @chrisbobbe for the Suggestion, have pushed the changes. PTAL.

[chrisbobbe]

Thanks! Just small comments below.

Also something I just noticed on this round: for the commit-message summary line, let's say

api: Accept unknown "emojiset" values in initial snapshot

[chrisbobbe]

We should aim to make the defaults boring and representative of real data, and I think Emojiset.google would be better for that than Emojiset.unknown.

[chrisbobbe]

Also this helper can deduplicate some code in the initialSnapshot helper just below this.

Just below the userSettings function declaration, you can say

const _userSettings = userSettings;

then in initialSnapshot in choosing arguments for the InitialSnapshot constructor, you can say:

    userSettings: userSettings ?? _userSettings(),