Start work on RPC endpoints for dealing with contact requests

Co-authored-by: Nathan Sobo <nathan@zed.dev>

crates/rpc/src/macros.rs

@@ -0,0 +1,67 @@
+#[macro_export]
+macro_rules! messages {
+    ($(($name:ident, $priority:ident)),* $(,)?) => {
+        pub fn build_typed_envelope(sender_id: ConnectionId, envelope: Envelope) -> Option<Box<dyn AnyTypedEnvelope>> {
+            match envelope.payload {
+                $(Some(envelope::Payload::$name(payload)) => {
+                    Some(Box::new(TypedEnvelope {
+                        sender_id,
+                        original_sender_id: envelope.original_sender_id.map(PeerId),
+                        message_id: envelope.id,
+                        payload,
+                    }))
+                }, )*
+                _ => None
+            }
+        }
+
+        $(
+            impl EnvelopedMessage for $name {
+                const NAME: &'static str = std::stringify!($name);
+                const PRIORITY: MessagePriority = MessagePriority::$priority;
+
+                fn into_envelope(
+                    self,
+                    id: u32,
+                    responding_to: Option<u32>,
+                    original_sender_id: Option<u32>,
+                ) -> Envelope {
+                    Envelope {
+                        id,
+                        responding_to,
+                        original_sender_id,
+                        payload: Some(envelope::Payload::$name(self)),
+                    }
+                }
+
+                fn from_envelope(envelope: Envelope) -> Option<Self> {
+                    if let Some(envelope::Payload::$name(msg)) = envelope.payload {
+                        Some(msg)
+                    } else {
+                        None
+                    }
+                }
+            }
+        )*
+    };
+}
+
+#[macro_export]
+macro_rules! request_messages {
+    ($(($request_name:ident, $response_name:ident)),* $(,)?) => {
+        $(impl RequestMessage for $request_name {
+            type Response = $response_name;
+        })*
+    };
+}
+
+#[macro_export]
+macro_rules! entity_messages {
+    ($id_field:ident, $($name:ident),* $(,)?) => {
+        $(impl EntityMessage for $name {
+            fn remote_entity_id(&self) -> u64 {
+                self.$id_field
+            }
+        })*
+    };
+}