has been blocked by CORS policy: Request header field abp.tenantid is not allowed by Access-Control-Allow-Headers in preflight response.

这个错误是由于CORS策略导致的。CORS（跨域资源共享）是一种浏览器安全机制，用于限制跨域请求。当你的前端应用从一个域名（例如localhost:8080）向另一个域名（例如localhost:3004）发起请求时，浏览器会发送一个预检请求（preflight request）来检查服务器是否允许跨域请求。预检请求会包含一些自定义的请求头字段，比如你提到的abp.tenantid。

根据你提供的引用内容，你可以解决这个问题的方法是在后端的响应头中设置允许前端请求时带有的字段值。你可以在Access-Control-Allow-Headers字段中添加abp.tenantid，以及其他你需要允许的自定义请求头字段。例如：

Access-Control-Allow-Headers: Content-Type, Access-Token, Appid, Secret, Authorization, abp.tenantid

这样，当浏览器发送预检请求时，服务器会返回允许的请求头字段列表，从而解决CORS策略导致的问题。
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