Add single asset vault (XLS-65d) (#5224)

- Specification: XRPLF/XRPL-Standards#239
- Amendment: `SingleAssetVault`
- Implements a vault feature used to store a fungible asset (XRP, IOU, or MPT, but not NFT) and to receive shares in the vault (an MPT) in exchange.
- A vault can be private or public.
- A private vault can use permissioned domains, subject to the `PermissionedDomains` amendment.
- Shares can be exchanged back into asset with `VaultWithdraw`.
- Permissions on the asset in the vault are transitively applied on shares in the vault.
- Issuer of the asset in the vault can clawback with `VaultClawback`.
- Extended `MPTokenIssuance` with `DomainID`, used by the permissioned domain on the vault shares.

Co-authored-by: John Freeman <jfreeman08@gmail.com>

include/xrpl/protocol/Asset.h

@@ -20,6 +20,7 @@
 #ifndef RIPPLE_PROTOCOL_ASSET_H_INCLUDED
 #define RIPPLE_PROTOCOL_ASSET_H_INCLUDED
 
+#include <xrpl/basics/Number.h>
 #include <xrpl/basics/base_uint.h>
 #include <xrpl/protocol/Issue.h>
 #include <xrpl/protocol/MPTIssue.h>
@@ -27,6 +28,7 @@
 namespace ripple {
 
 class Asset;
+class STAmount;
 
 template <typename TIss>
 concept ValidIssueType =
@@ -92,6 +94,9 @@ public:
     void
     setJson(Json::Value& jv) const;
 
+    STAmount
+    operator()(Number const&) const;
+
     bool
     native() const
     {
@@ -114,6 +119,14 @@ public:
     equalTokens(Asset const& lhs, Asset const& rhs);
 };
 
+inline Json::Value
+to_json(Asset const& asset)
+{
+    Json::Value jv;
+    asset.setJson(jv);
+    return jv;
+}
+
 template <ValidIssueType TIss>
 constexpr bool
 Asset::holds() const
@@ -219,9 +232,6 @@ validJSONAsset(Json::Value const& jv);
 Asset
 assetFromJson(Json::Value const& jv);
 
-Json::Value
-to_json(Asset const& asset);
-
 }  // namespace ripple
 
 #endif  // RIPPLE_PROTOCOL_ASSET_H_INCLUDED