Fix adding user properties to UserInfo context

[Arciiix]

I have noticed another bug related to user preferences. #242 that I pushed yesterday fixes saving those user preferences to the database, but they are still not loaded into the UserInfo context, therefore they are not accessible from any of the messaging integrations.

To reproduce, you can again set up the Telegram integration and add a breakpoint here:

notifo/backend/src/Notifo.Domain.Integrations/Telegram/TelegramIntegration.Messaging.cs

Lines 25 to 33 in fe94068

	public void AddTargets(IDictionary<string, string> targets, UserInfo user)
	{
	var chatId = GetChatId(user);
	if (!string.IsNullOrWhiteSpace(chatId))
	{
	targets[TelegramChatId] = chatId;
	}
	}

No matter what the user preferences are, the chatId will always be empty (because it doesn't exist in the Properties of UserInfo instance).

My fix merges the SystemProperties field together with the UserProperties, prioritizing the SystemProperties (therefore the .Last()) - because they were what was previously being set there - to ensure this fix doesn't break anything.

All the tests related to this are passing.

PS: I'm finishing the Discord integration. I'm doing those small pull requests that are general fixes not related to the integration itself, so that those changes are atomic (as you suggested in #38 ).

Have a nice day!

[SebastianStehle]

I am not a big fan of LINQ in this case. Can we just make it with a normal dictionary like

var properties = new Dictionary<string, string>(user.Properties);

if (user.SystemProperties != null)
{
   foreach (var (key, value) in user.SystemProperties)
   {
      properties[key] = values;
   } 
}

[Arciiix]

Sure, of course. Pushing the new changes...

[SebastianStehle]

See my comment

[SebastianStehle]

Btw: Notifo test coverage is really bad. Feel free to add new tests