ruby-authenticationlisted

# Authenticating an APIMatic Ruby SDK client How you authenticate depends on the security scheme(s) the API uses. APIMatic surfaces **one named parameter per scheme on `Client.new`**, and — for every scheme except custom authentication — **an immutable credentials class to pass to it** (see `ruby-client-initialization`). > **Custom authentication is the exception.** Its file holds only the scheme class (e.g. > `class CustomAuth < CoreLibrary::HeaderAuth`), built from the whole configuration and shipped as a > stub for the SDK's maintainer to complete. There is **no `{SchemeCredentials}` class to build**, even > though the `{scheme}_credentials:` parameter still exists. Check the scheme's file for a credentials > class before writing the call — a custom scheme means the SDK has to be completed or regenerated, not > configured from your application. ## Finding which schemes this SDK accepts Three places, in order of directness: 1. `lib/paypal_server_sdk/configuration.rb` — the credential parameters on `Configuration#initialize`. **These are the source of truth**; the same parameters appear on `Client#initialize`. 2. `lib/paypal_server_sdk/http/auth/` — one file per scheme, each holding the scheme class and, for every scheme but custom authentication, its `{SchemeCredentials}` data class. The credentials class is a **sibling** of the scheme class in the same module, not nested inside it, so it is referenced as `PaypalServerSdk::{SchemeCredentials}`. A file with