Change new_tx return type to String

src/api.rs

@@ -84,7 +84,7 @@ use crate::{
 pub struct ApiReturn {
     pub updated_cached_msg: Vec<CachedMessage>,
     pub updated_process: Option<(String, Process)>,
-    pub new_tx_to_send: Option<Transaction>,
+    pub new_tx_to_send: Option<String>,
     pub ciphers_to_send: Vec<String>,
     pub commit_to_send: Option<CommitMessage>,
 }
@@ -1324,7 +1324,7 @@ pub fn create_update_transaction(
     });
 
     Ok(ApiReturn {
-        new_tx_to_send: Some(final_tx),
+        new_tx_to_send: Some(serialize(&final_tx).to_lower_hex_string()),
         updated_process: Some((commitment_outpoint.to_string(), relevant_process.clone())),
         ciphers_to_send: ciphers,
         ..Default::default()