Add Assign Companies Feature for Customers

- Introduced a new endpoint to assign companies to a customer, enhancing the customer management capabilities.
- Implemented the AssignCompanies handler in the customer service layer, including validation and structured responses.
- Updated the routes to include the new PATCH /admin/v1/customers/{id}/companies endpoint, improving administrative functionalities.
- Enhanced API documentation with Swagger comments for the new endpoint, ensuring clarity for API consumers.

internal/customer/handler.go

@@ -265,6 +265,37 @@ func (h *Handler) AssignRole(c echo.Context) error {
 	return response.Success(c, result, "Role assigned successfully")
 }
 
+// AssignCompanies assigns companies to a customer
+// @Summary Assign companies to a customer
+// @Description Assign companies to a customer
+// @Tags Admin-Customers
+// @Accept json
+// @Produce json
+// @Param id path string true "Customer ID"
+// @Param companies body AssignCompaniesForm true "Companies to assign"
+// @Success 200 {object} response.APIResponse "Companies assigned successfully"
+// @Failure 400 {object} response.APIResponse "Bad request - Invalid input data"
+// @Failure 422 {object} response.APIResponse "Validation error - Invalid request data"
+// @Failure 500 {object} response.APIResponse "Internal server error"
+// @Security BearerAuth
+// @Router /admin/v1/customers/{id}/companies [patch]
+func (h *Handler) AssignCompanies(c echo.Context) error {
+	id := c.Param("id")
+	form, err := response.Parse[AssignCompaniesForm](c)
+	if err != nil {
+		return response.ValidationError(c, "Invalid request data", err.Error())
+	}
+
+	err = h.service.AssignCompanies(c.Request().Context(), id, form.Companies)
+	if err != nil {
+		return response.InternalServerError(c, "Failed to assign companies to customer")
+	}
+
+	return response.Success(c, map[string]interface{}{
+		"message": "Companies assigned successfully",
+	}, "Companies assigned successfully")
+}
+
 // **************************************************
 // *                 PROFILE HANDLERS               *
 // **************************************************