UnknownEvent: Create UnknownEvent to handle unknown event types to the specification.

Author: hikingc

src/main/java/io/github/hikingc/matrixsdk/api/events/ClientEvent.java

@@ -2,6 +2,7 @@
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import io.github.hikingc.matrixsdk.api.events.server.UnknownEvent;
 import io.github.hikingc.matrixsdk.api.identifiers.EventID;
 import io.github.hikingc.matrixsdk.api.identifiers.RoomID;
 import io.github.hikingc.matrixsdk.api.identifiers.UserID;
@@ -14,9 +15,13 @@
 /// @see <a href="https://spec.matrix.org/latest/client-server-api/#room-event-format">The room
 ///   event format as defined in the specification.</a>
 @JsonInclude(JsonInclude.Include.NON_ABSENT)
-@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
+@JsonTypeInfo(
+    use = JsonTypeInfo.Id.NAME,
+    include = JsonTypeInfo.As.PROPERTY,
+    property = "type",
+    defaultImpl = UnknownEvent.class)
 // This interface CANNOT permit anything other than these two.
-public sealed interface ClientEvent<T> permits StateEvent, MessageEvent {
+public sealed interface ClientEvent<T> permits StateEvent, MessageEvent, UnknownEvent {
 
   /// @return the body of this event, as created by the user which sent it.
   T content();

src/main/java/io/github/hikingc/matrixsdk/api/events/server/UnknownEvent.java

@@ -0,0 +1,17 @@
+package io.github.hikingc.matrixsdk.api.events.server;
+
+import io.github.hikingc.matrixsdk.api.events.ClientEvent;
+import io.github.hikingc.matrixsdk.api.events.UnsignedData;
+import io.github.hikingc.matrixsdk.api.identifiers.EventID;
+import io.github.hikingc.matrixsdk.api.identifiers.RoomID;
+import io.github.hikingc.matrixsdk.api.identifiers.UserID;
+
+public record UnknownEvent(
+    Object content,
+    EventID eventId,
+    Long originServerTs,
+    RoomID roomId,
+    UserID sender,
+    String type,
+    UnsignedData unsigned)
+    implements ClientEvent<Object> {}