title: Cookie created using express doesn't show in nextjs app
body: <p>I'm using <code>next-auth</code> to authenticate users in a NextJS app, when authenticated the express api sets a token cookie that I want to use later for api routes protection. Now the authentication works, but the cookie doesn't get saved in the cookie storage in the browser although it does on Postman.</p>
  <p>here's my credentials provider code</p>
  <pre class="lang-js prettyprint-override"><code>CredentialsProvider({
              async authorize(credentials) {
                      try {
                          const {data} = await axios.post(`${process.env.URL}/api/v1/auth/login`, {
                              email: credentials.email,
                              password: credentials.password,
                          }, {
                              headers: {
                                  'Content-Type': 'application/json'
                              }
                          })
  
                          if (data) {
                              return {
                                  username: data.username,
                                  email: data.email,
                              }
                          } else {
                              return null
                          }
                      } catch (error) {
                          return null
                      }
              }
          })
  </code></pre>