Make fields of RawNetworkMessage non public

provide accessor method and new for downstream libs.
This is done in order to more easily change the struct without impacting
downstream and also in order to add another field while preserving struct
invariant in future commit.

bitcoin/src/network/message.rs

@@ -149,10 +149,8 @@ crate::error::impl_std_error!(CommandStringError);
 /// A Network message
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub struct RawNetworkMessage {
-    /// Magic bytes to identify the network these messages are meant for
-    pub magic: Magic,
-    /// The actual message data
-    pub payload: NetworkMessage,
+    magic: Magic,
+    payload: NetworkMessage,
 }
 
 /// A Network message payload. Proper documentation is available on at
@@ -302,6 +300,22 @@ impl NetworkMessage {
 }
 
 impl RawNetworkMessage {
+
+    /// Creates a [RawNetworkMessage]
+    pub fn new(magic: Magic, payload: NetworkMessage) -> Self {
+        Self { magic, payload }
+    }
+
+    /// The actual message data
+    pub fn payload(&self) -> &NetworkMessage {
+        &self.payload
+    }
+
+    /// Magic bytes to identify the network these messages are meant for
+    pub fn magic(&self) -> &Magic {
+        &self.magic
+    }
+
     /// Return the message command as a static string reference.
     ///
     /// This returns `"unknown"` for [NetworkMessage::Unknown],