Manage DocuSign embedded signing (recipient view) URL and OAuth session lifecycle, including the 5-minute view-URL and 1-hour JWT token expiry

Steps

1. Obtain an OAuth access token via JWT Grant; this token expires after 1 hour and DocuSign does not issue a refresh token for the JWT flow, so long-running services must re-run the JWT assertion rather than expect a refresh token.
2. Create the envelope with the target recipient flagged as embedded by setting clientUserId on that recipient.
3. Call createRecipientView (POST /envelopes/{envelopeId}/views/recipient) with the recipient's clientUserId, returnUrl, and authentication method to obtain a one-time signing URL.
4. Redirect the recipient's browser to the returned URL immediately - it is single-use and expires about 5 minutes after being generated if not opened.
5. If the recipient doesn't launch the view in time, don't reuse the stale URL - issue a fresh createRecipientView call to generate a new one.
6. Inspect the event query parameter on your returnUrl callback (e.g., signing_complete, decline, ttl_expired) to detect an expired or abandoned session and trigger regeneration.