Access consumer financial data via the FDX v6 API using OAuth 2.0 FAPI 2.0 (Blue Profile) with PAR and PKCE

Steps

1. Register your Data Recipient (DR) application with the Financial Institution's (FI) developer portal and obtain a client_id; request the fdx:accountbasic, fdx:accountdetailed, fdx:transactions, and fdx:statements scopes appropriate for your use case
2. Use Pushed Authorization Requests (PAR): POST the authorization request to the FI's /par endpoint with code_challenge (PKCE S256), scope, redirect_uri, and state; receive a request_uri valid for a short lifetime
3. Redirect the user to the FI's authorization endpoint with only client_id and the request_uri from the PAR response; the user authenticates and grants consent
4. Exchange the authorization code for tokens at /token using client_assertion (private_key_jwt) rather than a client_secret; store the access_token and refresh_token
5. Call GET /fdx/v6/accounts to list accounts, then GET /fdx/v6/accounts/{accountId}/transactions with startTime and endTime query parameters (ISO 8601 format) to retrieve transactions
6. Implement consent introspection via POST /fdx/v6/consents/{consentId} to verify scope and expiry before each data fetch; revoke consent on user request via DELETE /fdx/v6/consents/{consentId}