Make Topic a newtype

Turns out having anything with any sort of lifetime in stream/sink
chains will trigger nasty issues such as
rust-lang/rust#79648 which is pretty difficult
to figure out how to work around.

Making `Topic` a newtype erases the lifetime from the type, making it
significantly easier to work with in thsoe contexts.

src/lib.rs

@@ -106,20 +106,17 @@
 #![cfg_attr(docsrs, feature(doc_cfg))]
 
 use std::{collections::BTreeMap, time::SystemTime};
-
+pub use topic::Topic;
 use uuid::Uuid;
 
 #[cfg(feature = "publish")]
 #[cfg_attr(docsrs, doc(cfg(feature = "publish")))]
 pub mod publish;
-
 #[cfg(test)]
 mod tests;
+mod topic;
 pub mod validators;
 
-/// A message queue topic name to which messages can be published
-pub type Topic = &'static str;
-
 /// All errors that may be returned when operating top level APIs.
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]

src/publish/mod.rs

@@ -185,7 +185,7 @@ where
             None => None,
             Some(stream_item) => Some((
                 stream_item,
-                this.topic,
+                *this.topic,
                 this.messages
                     .next()
                     .expect("should be as many messages as publishes"),

src/publish/publishers/null.rs

@@ -20,7 +20,7 @@ impl Publisher for NullPublisher {
     type MessageError = std::convert::Infallible;
     type PublishStream = NullPublishStream;
 
-    fn publish<'a, I>(&self, _: &'static str, messages: I) -> Self::PublishStream
+    fn publish<'a, I>(&self, _: crate::Topic, messages: I) -> Self::PublishStream
     where
         I: Iterator<Item = &'a ValidatedMessage> + ExactSizeIterator,
     {

src/topic.rs

@@ -0,0 +1,21 @@
+/// A message queue topic name to which messages can be published
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+pub struct Topic(pub &'static str);
+
+impl std::fmt::Display for Topic {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        std::fmt::Display::fmt(self.0, f)
+    }
+}
+
+impl From<&'static str> for Topic {
+    fn from(s: &'static str) -> Topic {
+        Topic(s)
+    }
+}
+
+impl From<Topic> for &'static str {
+    fn from(s: Topic) -> &'static str {
+        s.0
+    }
+}