token-2022: Add scaled amount extension (#7511)

* token-2022: Add scaled amount extension

#### Problem

The interest-bearing extension is useful for tokens that accrue in value
constantly, but many "rebasing" tokens on other blockchains employ a
different method of updating the number of tokens in accounts.

Rather than setting a rate and allowing the number to change
automatically over time, they set a scaling factor for the tokens by
hand.

#### Summary of changes

Add a new `ScaledUiAmount` extension to token-2022 for doing just that.
This is essentially a simplified version of the interest-bearing
extension, where someone just sets a scaling value into the mint
directly. The scale has no impact on the operation of the token, just on
the output of `amount_to_ui_amount` and `ui_amount_to_amount`.

* Add timestamp, rename to "multiplier"

* Update token/program-2022/src/extension/scaled_ui_amount/mod.rs

Co-authored-by: samkim-crypto <[email protected]>

* Address feedback

---------

Co-authored-by: samkim-crypto <[email protected]>

token/client/src/token.rs

@@ -43,8 +43,9 @@ use {
                 ConfidentialTransferFeeConfig,
             },
             cpi_guard, default_account_state, group_member_pointer, group_pointer,
-            interest_bearing_mint, memo_transfer, metadata_pointer, transfer_fee, transfer_hook,
-            BaseStateWithExtensions, Extension, ExtensionType, StateWithExtensionsOwned,
+            interest_bearing_mint, memo_transfer, metadata_pointer, scaled_ui_amount, transfer_fee,
+            transfer_hook, BaseStateWithExtensions, Extension, ExtensionType,
+            StateWithExtensionsOwned,
         },
         instruction, offchain,
         solana_zk_sdk::{
@@ -188,6 +189,10 @@ pub enum ExtensionInitializationParams {
         authority: Option<Pubkey>,
         member_address: Option<Pubkey>,
     },
+    ScaledUiAmountConfig {
+        authority: Option<Pubkey>,
+        multiplier: f64,
+    },
 }
 impl ExtensionInitializationParams {
     /// Get the extension type associated with the init params
@@ -207,6 +212,7 @@ impl ExtensionInitializationParams {
             }
             Self::GroupPointer { .. } => ExtensionType::GroupPointer,
             Self::GroupMemberPointer { .. } => ExtensionType::GroupMemberPointer,
+            Self::ScaledUiAmountConfig { .. } => ExtensionType::ScaledUiAmount,
         }
     }
     /// Generate an appropriate initialization instruction for the given mint
@@ -316,6 +322,15 @@ impl ExtensionInitializationParams {
                 authority,
                 member_address,
             ),
+            Self::ScaledUiAmountConfig {
+                authority,
+                multiplier,
+            } => scaled_ui_amount::instruction::initialize(
+                token_program_id,
+                mint,
+                authority,
+                multiplier,
+            ),
         }
     }
 }
@@ -1805,6 +1820,31 @@ where
         .await
     }
 
+    /// Update multiplier
+    pub async fn update_multiplier<S: Signers>(
+        &self,
+        authority: &Pubkey,
+        new_multiplier: f64,
+        new_multiplier_effective_timestamp: i64,
+        signing_keypairs: &S,
+    ) -> TokenResult<T::Output> {
+        let signing_pubkeys = signing_keypairs.pubkeys();
+        let multisig_signers = self.get_multisig_signers(authority, &signing_pubkeys);
+
+        self.process_ixs(
+            &[scaled_ui_amount::instruction::update_multiplier(
+                &self.program_id,
+                self.get_address(),
+                authority,
+                &multisig_signers,
+                new_multiplier,
+                new_multiplier_effective_timestamp,
+            )?],
+            signing_keypairs,
+        )
+        .await
+    }
+
     /// Update transfer hook program id
     pub async fn update_transfer_hook_program_id<S: Signers>(
         &self,