Update FileSystemPersister to work with Windows.

    Mainly, use std::path::Path so that the constructed paths
    are OS-agnostic.

    Also, Windows necessitates the use of OpenOptions with the `write`
    permission enabled to `sync_all` on a newly opened channel's
    data file.

Author: valentinewallace

lightning-data-persister/src/lib.rs

@@ -60,7 +60,10 @@ impl<ChanSigner: ChannelKeys + Readable + Writeable> FilesystemPersister<ChanSig
 	}
 
 	fn get_full_filepath(&self, funding_txo: OutPoint) -> String {
-		format!("{}/{}_{}", self.path_to_channel_data, funding_txo.txid.to_hex(), funding_txo.index)
+		let path = Path::new(&self.path_to_channel_data);
+		let mut path_buf = path.to_path_buf();
+		path_buf.push(format!("{}_{}", funding_txo.txid.to_hex(), funding_txo.index));
+		path_buf.to_str().unwrap().to_string()
 	}
 
 	// Utility to write a file to disk.