🌿 ✨ [Scheduled] Update API Spec (#64)

* fix(api): add firstMessage field to OpenAPI spec

* feat(openapi): add knowledge base endpoints and inflection ai support

* feat(stripe): added pending status and invoice ID to payment object

* fix(openapi): update maximum silence duration and rename schemas

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Co-authored-by: fern-api[bot] <115122769+fern-api[bot]@users.noreply.github.com>
Co-authored-by: Rajdeep Ghosh <[email protected]>