fix(server): prevent delete base currency

packages/server/src/services/Currencies/CurrencyTransformer.ts

@@ -0,0 +1,19 @@
+import { Transformer } from '@/lib/Transformer/Transformer';
+
+export class CurrencyTransformer extends Transformer {
+  /**
+   * Include these attributes to sale invoice object.
+   * @returns {Array}
+   */
+  public includeAttributes = (): string[] => {
+    return ['isBaseCurrency'];
+  };
+
+  /**
+   * Detarmines whether the currency is base currency.
+   * @returns {boolean}
+   */
+  public isBaseCurrency(currency): boolean {
+    return this.context.organization.baseCurrency === currency.currencyCode;
+  }
+}