a8d53a6df4
Linear is deprecating long-lived OAuth2 access tokens (valid for 10 years) in favor of short-lived access tokens with refresh tokens. Starting October 1, 2025, all new OAuth2 apps will default to refresh tokens. Linear will no longer issue long-lived access tokens. Please read more details [here](https://linear.app/developers/oauth-2-0-authentication#migrate-to-using-refresh-tokens) We currently use long-lived tokens in our Linear integration (valid for up to 10 years). To remain compatible, this PR ensures compatibility by supporting refresh-token-based auth and migrating existing legacy tokens. Fixes https://linear.app/chatwoot/issue/CW-5541/migrate-linear-oauth2-integration-to-support-refresh-tokens