handle form submit stream registration

App2.js

//frontend/src/App.js:15
 const register = async (e) => {
    try {
      e.preventDefault();
      var response = await fetch('http://localhost:8080/registrations', {
        method: 'POST',
        headers: {
          'Accept': 'application/json',
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          firstName,
          lastName,
          email,
        }),
      });
    // ...
    } catch (err) {
        console.error(err)
    }