Getting '400 (Bad Request)' error when making a POST request to backend API

'm encountering an issue where I'm getting a '400 (Bad Request)' error when attempting to make a POST request to my backend API. I'm using Axios in my Vue.js application to send the request. Here's my code snippet:

import axios from "axios";

export default {
  data() {
    return {
      users: [],
      api: "http://127.0.0.1:8000",
      user: {
        firstName: "",
        lastName: "",
        email: "",
        affiliation: "",
        occupation: "",
        reason: "",
      },
    };
  },
  methods: {
    submitForm(e1) {
      e1.preventDefault();
      // Send the form data to the backend API endpoint
      axios
        .post(this.api + "/user/", {
          firstName: this.user.firstName,
          lastName: this.user.lastName,
          email: this.user.email,
          affiliation: this.user.affiliation,
          occupation: this.user.occupation,
          reason: this.user.reason,
        })
        .then((response) => {
          console.log(response.data);
          // this.user = {}; // Handle the response
        })
        .catch((error) => {
          console.error(error); // Handle any errors
        });
      // console.log(this.api + "/user/", this.user);
    },
  },
};

I've double-checked the request payload and confirmed that all the required fields are included and in the correct format. However, the server responds with a '400 (Bad Request)' status code.

I've also verified that the API endpoint URL (this.api + "/user/") is correct and matches the backend route that expects the POST request.

I'm unsure how to proceed with troubleshooting this issue. Could you please provide some guidance on possible causes for this error and steps I can take to resolve it?

Thank you in advance for your assistance!

Here are a few of the troubleshooting steps I would take

1. I would try to log out the request on the server. Does the request coming in from the frontend look like you expect it? Often when i see this kind of problem, the request body is surprising and that insight helps me discover the real problem.

2. I would confirm that the request format that you are sending matches the format your server is expecting. For example, your server may be expecting form data but you are sending json. This often is sent across automatically in the header.

One way that I like to verify this is to make the request in the browser and then go to the network tab and right click on the request. There should be a "copy as CURL" option. Make that request from the terminal and you should see the same result. Now go to a tool like postman and try to send a request using the same body data that your curl command is sending. Do you see the same result? If not, you likely now know that it may be that your content-type header is incorrect. Using different tools helps me sanity check what part of the data I'm sending to the server is causing the problem. Once you know which part of your data is causing the issue, troubleshooting from there should be much easier for you.

So in short, check that the headers and body are what you expect them to be on the server, and that the libraries you have imported on your server support the body format you expect.