fix: resolve CheckoutSessions Invalid URL error

Fix URL construction creating double slashes in CheckoutSessions endpoints.
Updated basePath handling to prevent malformed URLs like https://api.pay.magpie.im//cs_123.

Author: donjerick

src/resources/base.ts

@@ -43,7 +43,16 @@ export abstract class BaseResource {
    * @protected
    */
   protected buildPath(id?: string): string {
-    return id ? `${this.basePath}/${id}` : this.basePath;
+    if (!id) {
+      return this.basePath;
+    }
+    
+    // Handle empty basePath (used for resources with custom base URLs)
+    if (this.basePath === '') {
+      return id;
+    }
+    
+    return `${this.basePath}/${id}`;
   }
 
   /**

src/resources/sessions.test.ts

@@ -23,7 +23,7 @@ describe('CheckoutSessionsResource', () => {
 
       expect(magpie.LAST_REQUEST).toMatchObject({
         method: 'POST',
-        url: expect.stringContaining('/'),
+        url: expect.stringContaining(''),
         data: sessionData
       });
     });
@@ -86,7 +86,7 @@ describe('CheckoutSessionsResource', () => {
 
       expect(magpie.LAST_REQUEST).toMatchObject({
         method: 'GET',
-        url: expect.stringContaining(`/${sessionId}`)
+        url: expect.stringContaining(sessionId)
       });
     });
 
@@ -116,7 +116,7 @@ describe('CheckoutSessionsResource', () => {
 
       expect(magpie.LAST_REQUEST).toMatchObject({
         method: 'POST',
-        url: expect.stringContaining(`/${sessionId}/capture`),
+        url: expect.stringContaining(`${sessionId}/capture`),
         data: captureData
       });
     });
@@ -154,7 +154,7 @@ describe('CheckoutSessionsResource', () => {
 
       expect(magpie.LAST_REQUEST).toMatchObject({
         method: 'POST',
-        url: expect.stringContaining(`/${sessionId}/expire`)
+        url: expect.stringContaining(`${sessionId}/expire`)
       });
     });
 

src/resources/sessions.ts

@@ -44,7 +44,7 @@ export class CheckoutSessionsResource extends BaseResource {
    */
   constructor(client: BaseClient) {
     // Use different base URL for checkout sessions
-    super(client, '/', 'https://api.pay.magpie.im');
+    super(client, '', 'https://api.pay.magpie.im');
   }
 
   /**