title: How to upload files and attachments to the sobject record using REST API?
body: <p>Salesforce has two different UIs and in accordance with it, it has the possibility to store attached files differently.
  Two files were uploaded via the classic UI and they are marked as 'attachments'. Other files were uploaded through the new UI and they are marked as 'files'.
  I want to upload all of these files using REST API. I cannot find the proper documentation. Can somebody help me with this?</p>