feat(monetization): add get entitlement endpoint

Author: Jiralite

packages/core/src/api/monetization.ts

@@ -14,6 +14,9 @@ import {
 	type Snowflake,
 } from 'discord-api-types/v10';
 
+// TODO: discord-api-types
+type RESTGetAPIEntitlementResult = RESTGetAPIEntitlementsResult[number];
+
 export class MonetizationAPI {
 	public constructor(private readonly rest: REST) {}
 
@@ -84,6 +87,24 @@ export class MonetizationAPI {
 		}) as Promise<RESTGetAPIEntitlementsResult>;
 	}
 
+	/**
+	 * Fetches an entitlement for an application.
+	 *
+	 * @see {@link https://discord.com/developers/docs/resources/entitlement#get-entitlement}
+	 * @param applicationId - The application id to fetch the entitlement for
+	 * @param entitlementId - The entitlement id to fetch
+	 * @param options - The options for fetching the entitlement
+	 */
+	public async getEntitlement(
+		applicationId: Snowflake,
+		entitlementId: Snowflake,
+		{ signal }: Pick<RequestData, 'signal'> = {},
+	) {
+		return this.rest.get(Routes.entitlement(applicationId, entitlementId), {
+			signal,
+		}) as Promise<RESTGetAPIEntitlementResult>;
+	}
+
 	/**
 	 * Creates a test entitlement for an application's SKU.
 	 *