Move some trait implementation under the test module

They were only implemented if the test cfg flag was enabled and used in
the test module so it makes more sense that they are in the test module
as well.

src/olm/messages/mod.rs

@@ -148,36 +148,11 @@ impl From<MessageType> for usize {
     }
 }
 
-#[cfg(test)]
-use olm_rs::session::OlmMessage as LibolmMessage;
-
-#[cfg(test)]
-impl From<LibolmMessage> for OlmMessage {
-    fn from(other: LibolmMessage) -> Self {
-        let (message_type, ciphertext) = other.to_tuple();
-        let ciphertext_bytes = base64_decode(ciphertext).expect("Can't decode base64");
-
-        Self::from_parts(message_type.into(), ciphertext_bytes.as_slice())
-            .expect("Can't decode a libolm message")
-    }
-}
-
-#[cfg(test)]
-impl From<OlmMessage> for LibolmMessage {
-    fn from(value: OlmMessage) -> LibolmMessage {
-        match value {
-            OlmMessage::Normal(m) => LibolmMessage::from_type_and_ciphertext(1, m.to_base64())
-                .expect("Can't create a valid libolm message"),
-            OlmMessage::PreKey(m) => LibolmMessage::from_type_and_ciphertext(0, m.to_base64())
-                .expect("Can't create a valid libolm pre-key message"),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use anyhow::Result;
     use assert_matches::assert_matches;
+    use olm_rs::session::OlmMessage as LibolmMessage;
     use serde_json::json;
 
     use super::*;
@@ -201,6 +176,27 @@ mod tests {
     const MESSAGE_CIPHERTEXT: [u8; 16] =
         [249, 125, 179, 111, 185, 4, 95, 253, 201, 190, 130, 236, 165, 195, 65, 112];
 
+    impl From<OlmMessage> for LibolmMessage {
+        fn from(value: OlmMessage) -> LibolmMessage {
+            match value {
+                OlmMessage::Normal(m) => LibolmMessage::from_type_and_ciphertext(1, m.to_base64())
+                    .expect("Can't create a valid libolm message"),
+                OlmMessage::PreKey(m) => LibolmMessage::from_type_and_ciphertext(0, m.to_base64())
+                    .expect("Can't create a valid libolm pre-key message"),
+            }
+        }
+    }
+
+    impl From<LibolmMessage> for OlmMessage {
+        fn from(other: LibolmMessage) -> Self {
+            let (message_type, ciphertext) = other.to_tuple();
+            let ciphertext_bytes = base64_decode(ciphertext).expect("Can't decode base64");
+
+            Self::from_parts(message_type.into(), ciphertext_bytes.as_slice())
+                .expect("Can't decode a libolm message")
+        }
+    }
+
     #[test]
     fn message_type_from_usize() {
         assert_eq!(