Some of the APIs published on api.sap.com, require oAuth2 authentication. I am trying to understand how that can be enabled for S/4HANA Cloud. Most of the documentation that SAP has published, relates to extending a standard API on BTP and how that extension can call API using oAuth2 (https://help.sap.com/doc/6ce62b6bdda340ffbeae3f138c3cb71b/SHIP/en-US/Set_Up_Authentication_for_SAP_S4HANA_Cloud_Extensions.pdf).
Suppose, the standard API is to be called without using a BTP extension, how does oAuth2 work? How to setup communication arrangement, user & secret to enable oAuth2 API directly to S/4HANA Cloud, from any external system?
Since IAS is responsible for authenticating the users, is IAS setup required to enable oAuth2 API calls (https://help.sap.com/docs/IDENTITY_AUTHENTICATION/6d6d63354d1242d185ab4830fc04feb1/44b0d28cf4fa4fb29c3333e77bb719da.html)?
In ECC or OnPremise S/4HANA systems, there is a transaction code SOAUTH2 to setup Client ID for oAuth2 calls. What is the equivalent process for S/4HANA Cloud (not involving BTP extensions development)?