Allow the emitter to be mutable

This is the case when the emitter is the fee payer.

Change-Id: Ib21658c6cbbbb246a7434057c0f03f24bec8c013

solana/bridge/client/src/main.rs

@@ -134,14 +134,13 @@ fn command_post_message(
         fee,
     );
 
-    let emitter = Keypair::new();
     let message = Keypair::new();
     let ix = match proxy {
         Some(p) => cpi_poster::instructions::post_message(
             p,
             *bridge,
             config.owner.pubkey(),
-            emitter.pubkey(),
+            config.owner.pubkey(),
             message.pubkey(),
             nonce,
             payload,
@@ -151,7 +150,7 @@ fn command_post_message(
         None => bridge::instructions::post_message(
             *bridge,
             config.owner.pubkey(),
-            emitter.pubkey(),
+            config.owner.pubkey(),
             message.pubkey(),
             nonce,
             payload,
@@ -165,7 +164,7 @@ fn command_post_message(
     let (recent_blockhash, fee_calculator) = config.rpc_client.get_recent_blockhash()?;
     check_fee_payer_balance(config, fee_calculator.calculate_fee(&transaction.message()))?;
     transaction.sign(
-        &[&config.fee_payer, &config.owner, &emitter, &message],
+        &[&config.fee_payer, &config.owner, &message],
         recent_blockhash,
     );
     Ok(Some(transaction))

solana/bridge/program/src/api/post_message.rs

@@ -43,7 +43,7 @@ pub struct PostMessage<'b> {
     pub message: Signer<Mut<UninitializedMessage<'b>>>,
 
     /// Emitter of the VAA
-    pub emitter: Signer<Info<'b>>,
+    pub emitter: Signer<MaybeMut<Info<'b>>>,
 
     /// Tracker for the emitter sequence
     pub sequence: Mut<Sequence<'b>>,