refactoring: balance sheet report.

refactoring: trial balance sheet report.
refactoring: general ledger report.
refactoring: journal report.
refactoring: P&L report.

server/src/repositories/CachableRepository.ts

@@ -0,0 +1,19 @@
+import hashObject from 'object-hash';
+
+
+export default class CachableRepository {
+  repositoryName: string;
+ 
+  /**
+   * Retrieve the cache key of the method name and arguments.
+   * @param {string} method 
+   * @param {...any} args 
+   * @return {string}
+   */
+  getCacheKey(method, ...args) {
+    const hashArgs = hashObject({ ...args });
+    const repositoryName = this.repositoryName;
+
+    return `${repositoryName}-${method}-${hashArgs}`;
+  }
+}