feat: Working VoIP calling implementation (Flutter + Android)

Working video and audio calls, as well as android integration

lib/models/call_state.dart

@@ -0,0 +1,28 @@
+enum CallState {
+  Idle,
+  IncomingReceived,
+  PushIncomingReceived,
+  OutgoingInit,
+  OutgoingProgress,
+  OutgoingRinging,
+  OutgoingEarlyMedia,
+  Connected,
+  StreamsRunning,
+  Pausing,
+  Paused,
+  Resuming,
+  Referred,
+  Error,
+  End,
+  PausedByRemote,
+  UpdatedByRemote,
+  IncomingEarlyMedia,
+  Updating,
+  Released,
+  EarlyUpdatedByRemote,
+  EarlyUpdating;
+
+  static CallState fromOrdinal(int ordinal) {
+    return values[ordinal];
+  }
+}

lib/models/call_type.dart

@@ -0,0 +1,9 @@
+enum CallType {
+  Audio,
+  Video,
+  Unknown;
+
+  static CallType fromOrdinal(int ordinal) {
+    return values[ordinal];
+  }
+}

lib/models/registration_state.dart

@@ -0,0 +1,11 @@
+enum RegistrationState {
+  None,
+  Progress,
+  Ok,
+  Cleared,
+  Failed;
+
+  static RegistrationState fromOrdinal(int ordinal) {
+    return values[ordinal];
+  }
+}