MCP.OAuth2.Adapter behaviour (fnord v0.8.82)

Behaviour for DI-friendly OAuth2/OIDC Authorization Code + PKCE flow.

This behaviour abstracts the "start flow" step so tests can inject a mock implementation and production can perform real discovery/flow creation.

Responsibilities:

Provide a single entry point for beginning the auth flow and returning {port, state, verifier, auth_url, redirect_uri} semantics required by the loopback finalize path.

Introduced: M3 (OAuth CLI orchestration, DI boundary).

Summary

start_flow(map)

@callback start_flow(map()) ::
  {:ok, non_neg_integer(), String.t(), String.t(), String.t(), String.t()}
  | {:error, term()}