feat: support credit transfers and precious metal valuations

apps/api/src/movement.ts

@@ -1,15 +1,22 @@
 import Decimal from 'decimal.js';
 import { BadRequestException } from '@nestjs/common';
 export type Movement = 'transfer' | 'borrow' | 'lend' | 'collect' | 'repay';
-export function movementDeltas(operation: Movement, amount: string, received: string, fee: string) {
+export function movementDeltas(
+  operation: Movement,
+  amount: string,
+  received: string,
+  fee: string,
+  sourceSide = 'asset',
+  targetSide = 'asset',
+) {
   const incoming = operation === 'borrow' || operation === 'collect';
   const principal = new Decimal(amount),
     charge = new Decimal(fee),
     debt = new Decimal(received);
   if (operation === 'transfer')
     return {
-      source: principal.plus(charge).neg(),
-      target: debt,
+      source: principal.plus(charge).mul(sourceSide === 'liability' ? 1 : -1),
+      target: debt.mul(targetSide === 'liability' ? -1 : 1),
       sourceReason: 'transfer_out',
       targetReason: 'transfer_in',
     };