feat(callstatelib): add a callstate publishable lib

libs/shared/ngrx-callstate-store/src/lib/external.model.ts

@@ -0,0 +1,18 @@
+/* eslint-disable @typescript-eslint/no-empty-interface */
+import { ClassProvider, InjectionToken, Type } from '@angular/core';
+import { CallStateErrorHandler } from './call-state.model';
+
+export interface ErrorHandler<T extends CustomError> {
+  toError: (error: unknown) => T;
+  getErrorMessage: (error?: T) => string | undefined;
+}
+
+export interface CustomError {}
+
+export const ERROR_TOKEN = new InjectionToken<ErrorHandler<any>>('error', {
+  factory: () => new CallStateErrorHandler(),
+});
+
+export const provideErrorHandler = <T extends ErrorHandler<any>>(
+  errorHandlerClass: Type<T>
+): ClassProvider => ({ provide: ERROR_TOKEN, useClass: errorHandlerClass });