Implement From<AnyInitialStateEvent> on PduBuilder

The conversion between the two is now direct and thus shouldn't lose the state_keys.

src/pdu.rs

@@ -2,9 +2,9 @@ use crate::Error;
 use log::error;
 use ruma::{
     events::{
-        pdu::EventHash, room::member::MemberEventContent, AnyEphemeralRoomEvent, AnyRoomEvent,
-        AnyStateEvent, AnyStrippedStateEvent, AnySyncRoomEvent, AnySyncStateEvent, EventType,
-        StateEvent,
+        pdu::EventHash, room::member::MemberEventContent, AnyEphemeralRoomEvent,
+        AnyInitialStateEvent, AnyRoomEvent, AnyStateEvent, AnyStrippedStateEvent, AnySyncRoomEvent,
+        AnySyncStateEvent, EventType, StateEvent,
     },
     serde::{CanonicalJsonObject, CanonicalJsonValue, Raw},
     state_res, EventId, MilliSecondsSinceUnixEpoch, RoomId, RoomVersionId, ServerName,
@@ -346,3 +346,17 @@ pub struct PduBuilder {
     pub state_key: Option<String>,
     pub redacts: Option<EventId>,
 }
+
+/// Direct conversion prevents loss of the empty `state_key` that ruma requires.
+impl From<AnyInitialStateEvent> for PduBuilder {
+    fn from(event: AnyInitialStateEvent) -> Self {
+        Self {
+            event_type: EventType::from(event.event_type()),
+            content: serde_json::value::to_value(event.content())
+                .expect("AnyStateEventContent came from JSON and can thus turn back into JSON."),
+            unsigned: None,
+            state_key: Some(event.state_key().to_owned()),
+            redacts: None,
+        }
+    }
+}