release: 0.21.0

[stainless-app]

Automated Release PR

0.21.0 (2026-09-15)

Full Changelog: v0.20.0...v0.21.0

Features

• [CARDS-5174] Add reiusse/renew 409 error (2fc8f3b)
• Add missing blockchain/stablecoin endpoints to the spec (3e8c0dc)
• api: add EXTERNAL_STABLECOIN category and events to payment resources (518aebb)
• api: add OTHER enum value to auth_rules type field (1bb4cc8)
• api: add psd2_context field to three_ds_authentication (19e526e)
• api: add STABLECOIN_REVIEWED event type to payment simulate action (766c658)
• AUTH-3759: Add DECLINE_SCA_REQUIRED and SCA_REQUIRED enum entries (e784b27)
• TRE-14349: add installment plan management operation event types (bd71bde)
• TRE-14429: Document the stablecoin payments endpoint (050c7bd)

Documentation

• Document the card.pin_updated webhook (b96e92e)

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