Expose invite_user_by_id over the FFI

This PR is self explanatory.

Exposes said function to the FFI. Defined in the .adl file,
and defined to throw `ClientError`

Signed-off-by: Simon Farre <simon.farre.cx@gmail.com>
Co-authored-by: Damir Jelić <poljar@termina.org.uk>

bindings/matrix-sdk-ffi/src/api.udl

@@ -274,6 +274,9 @@ interface Room {
 
     [Throws=ClientError]
     void remove_avatar();
+
+    [Throws=ClientError]
+    void invite_user_by_id(string user_id);
 };
 
 callback interface TimelineListener {

bindings/matrix-sdk-ffi/src/room.rs

@@ -554,6 +554,20 @@ impl Room {
             Ok(())
         })
     }
+
+    pub fn invite_user_by_id(&self, user_id: String) -> Result<()> {
+        let room = match &self.room {
+            SdkRoom::Joined(joined_room) => joined_room.clone(),
+            _ => bail!("Can't invite user to room that isn't in joined state"),
+        };
+
+        RUNTIME.block_on(async move {
+            let user = <&UserId>::try_from(user_id.as_str())
+                .context("Could not create user from string")?;
+            room.invite_user_by_id(user).await?;
+            Ok(())
+        })
+    }
 }
 
 impl std::ops::Deref for Room {