feat: introduce Joi validation schemas and integrate them across various controllers for categories, lessons, courses, chapters, announcements, and admin course approvals.

Backend/src/validators/AdminCourseApproval.validator.ts

@@ -0,0 +1,30 @@
+import Joi from 'joi';
+
+/**
+ * Validator for approving a course
+ * Comment is optional
+ */
+export const ApproveCourseValidator = Joi.object({
+    comment: Joi.string()
+        .max(1000)
+        .optional()
+        .messages({
+            'string.max': 'Comment must not exceed 1000 characters'
+        })
+});
+
+/**
+ * Validator for rejecting a course
+ * Comment is required when rejecting
+ */
+export const RejectCourseValidator = Joi.object({
+    comment: Joi.string()
+        .min(10)
+        .max(1000)
+        .required()
+        .messages({
+            'string.min': 'Comment must be at least 10 characters when rejecting a course',
+            'string.max': 'Comment must not exceed 1000 characters',
+            'any.required': 'Comment is required when rejecting a course'
+        })
+});