Odoo requires users of the REST API to be authenticated before they can query most data.
restapi/1.0/common endpoint provides meta-calls which don’t require authentication, such as the authentication itself or fetching version information. To verify if the connection information is correct before trying to authenticate, the simplest call is to ask for the server’s version through the
restapi/1.0/common/version endpoint. The authentication itself is done through the OAuth 1.0
restapi/1.0/common/oauth1 or OAuth 2.0