Messenger example - send auth request

• Refactor user search
• Add contact feature
• Save found contacts
• Add send request feature
• Send auth request
• Fix saving my contact during registration

Examples/xx-messenger/Sources/AppCore/XXClientHelpers/XXContact+Helpers.swift

+import XXClient
+
+extension Contact {
+  public var username: String? {
+    try? getFacts().first(where: { $0.type == 0 })?.fact
+  }
+
+  public var email: String? {
+    try? getFacts().first(where: { $0.type == 1 })?.fact
+  }
+
+  public var phone: String? {
+    try? getFacts().first(where: { $0.type == 2 })?.fact
+  }
+}