/**
 * Payment Type Definitions
 *
 * Type definitions and validators for Stripe payment endpoints.
 *
 * @module controllers/payment/payment.types
 */
/** Valid subscription plan identifiers */
export declare const PLAN_IDS: readonly ["starter", "pro", "max"];
/** Plan ID type */
export type PlanId = (typeof PLAN_IDS)[number];
/** Valid billing intervals */
export declare const BILLING_INTERVALS: readonly ["month", "year"];
/** Billing interval type */
export type BillingInterval = (typeof BILLING_INTERVALS)[number];
/**
 * Check if a string is a valid plan ID.
 *
 * @param value - Value to check
 * @returns True if value is a valid PlanId
 */
export declare function isValidPlanId(value: string): value is PlanId;
/**
 * Check if a string is a valid billing interval.
 *
 * @param value - Value to check
 * @returns True if value is a valid BillingInterval
 */
export declare function isValidBillingInterval(value: string): value is BillingInterval;
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