refactor: use openAPI types for user info

[RLesser]

:rocket:	This description was created by Ellipsis for commit 52cfa490f0786459ce537fd2448f14f4cbb805aa

Summary:

This PR refines user and organization type definitions in the SDK, adds a new promo code validation endpoint, and updates the AtlasUser class to use specific types for improved type safety.

Key points:

• Updated src/type-gen/openapi.ts to include a new endpoint /v1/stripe/promo-code/validate for validating promo codes.
• Modified components['schemas']['Organization'] to use components['schemas']['OrganizationPlan'] for plan_type.
• Added components['schemas']['StripeSubscriptionCancelRequest and components['schemas']['ValidatePromoCodeRequest.
• Updated src/user.ts to use components['schemas']['PrivateUser'] in AtlasUser class.
• Removed deprecated OrganizationUserInfo and UserInfo types from src/user.ts.

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Generated with :heart: by ellipsis.dev

[RLesser]

• #68 👈
• main

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