解决这个问题的方法是在Angular的安全拦截器中添加认证头。下面是一个示例代码：

首先，在你的安全拦截器中创建一个HttpInterceptor类，它实现了HttpInterceptor接口。在拦截器中，你可以检查请求的类型，如果是POST请求，则添加认证头：

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
  intercept(request: HttpRequest, next: HttpHandler): Observable> {
    if (request.method === 'POST') {
      // 添加认证头
      const modifiedRequest = request.clone({
        setHeaders: {
          Authorization: 'Bearer your-auth-token'
        }
      });
      
      return next.handle(modifiedRequest);
    } else {
      return next.handle(request);
    }
  }
}

接下来，在你的NgModule中将这个拦截器提供给HTTP_INTERCEPTORS：

import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';

import { AuthInterceptor } from './auth.interceptor';

@NgModule({
  imports: [HttpClientModule],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true
    }
  ]
})
export class AppModule { }

现在，每次发送POST请求时，都会自动添加认证头。请记得将your-auth-token替换为你的实际认证令牌。