Redesign for the v1 stable release (#3)

Only half done. Will continue in another PR.

Reviewed-on: #3

crates/chat/src/room.rs

@@ -167,22 +167,11 @@ impl From<&UnsignedEvent> for Room {
 
 impl Room {
     /// Constructs a new room with the given receiver and tags.
-    pub fn new(subject: Option<String>, author: PublicKey, receivers: Vec<PublicKey>) -> Self {
-        // Convert receiver's public keys into tags
-        let mut tags: Tags = Tags::from_list(
-            receivers
-                .iter()
-                .map(|pubkey| Tag::public_key(pubkey.to_owned()))
-                .collect(),
-        );
-
-        // Add subject if it is present
-        if let Some(subject) = subject {
-            tags.push(Tag::from_standardized_without_cell(TagStandard::Subject(
-                subject,
-            )));
-        }
-
+    pub fn new<T>(author: PublicKey, receivers: T) -> Self
+    where
+        T: IntoIterator<Item = PublicKey>,
+    {
+        let tags = Tags::from_list(receivers.into_iter().map(Tag::public_key).collect());
         let mut event = EventBuilder::new(Kind::PrivateDirectMessage, "")
             .tags(tags)
             .build(author);