If you are afraid of your password being stolen by a malicious proxy or by MySiga server, you can do a POST request to the end-point /login/raw where you will need to encrypt your password before sending it, as it adds a lot of complexity it will not be covered in this quick tutorial.
With your CPF and password ready, u can prepare and send the login request like so:
Now you're logged, so let's do a GET request to /academic/registration/browser end-point, this only requires the PHPSESSID cookie to be sent so it knows who u are, the PHPSESSID value is the same as the "client" field on the login response.
curl --request GET \
--url https://mysiga.laravieira.me/academic/registration/browser \
--cookie 'PHPSESSID=1e1a3a2698a6ac2fb0bbe8867f713e09'
If you are using the browser or an API tester, the registration pdf will show up.
If you are not using a browser or an API tester, you may see the raw pdf data of the registration file, you can save this data to a file, set the extension of that file to .pdf, and then open it normally.
Extra step
If you are a person who loves to click on the logout button, u can also send a GET request to /login/logout destroy your session on the MySiga and on Siga 3. This also requires u to send the PHPSESSID, so MySiga knows which session to destroy. Do it like this:
curl --request GET \
--url https://mysiga.laravieira.me/login/logout \
--cookie 'PHPSESSID=1e1a3a2698a6ac2fb0bbe8867f713e09'