Add checkout data and user orders REST APIs

[syedgalib]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Security fix
• Improvement
• New Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Text changes
• Other... Please describe:

Description

Why this PR is needed

Clients need a provider-aware checkout URL and authenticated order APIs that never accept an arbitrary user ID. Extensions also need a safe way to replace order operations before Directorist writes data.

What is done in this PR

• Adds GET /directorist/v2/checkout with filterable provider data.
• Adds authenticated create, single-order, and paginated collection operations under /directorist/v2/orders.
• Uses the current session user for every user order operation and enforces order and listing ownership.
• Wraps order results with the Directorist provider type and exposes pagination totals through WordPress REST headers.
• Adds short-circuit hooks for alternate order providers and fixes one-item pagination in the order repository.

How to test the PR

1. Activate Directorist, authenticate as a user, and request GET /wp-json/directorist/v2/checkout; verify the response type is directorist and the URL is the configured checkout page.
2. POST an order to /wp-json/directorist/v2/orders without a user ID; verify the created order belongs to the authenticated user and the response has order_type directorist.
3. GET /wp-json/directorist/v2/orders/{id}; verify users can read only their own order.
4. GET /wp-json/directorist/v2/orders?page=1&per_page=1; verify one order is returned and X-WP-Total and X-WP-TotalPages are correct.

Any linked issues

N/A

Checklist

• My code follows the WordPress coding standards