how to add an admin form customer email dropdown in magento 2

1define([
2    'Magento_Ui/js/form/element/ui-select'
3], function (Select) {
4    'use strict';
5    return Select.extend({
6        /**
7         * Parse data and set it to options.
8         *
9         * @param {Object} data - Response data object.
10         * @returns {Object}
11         */
12        setParsed: function (data) {
13            var option = this.parseData(data);
14            if (data.error) {
15                return this;
16            }
17            this.options([]);
18            this.setOption(option);
19            this.set('newOption', option);
20        },
21        /**
22         * Normalize option object.
23         *
24         * @param {Object} data - Option object.
25         * @returns {Object}
26         */
27        parseData: function (data) {
28            return {
29                value: data.customer.entity_id,
30                label: data.customer.name
31            };
32        }
33    });
34});
35

1<?php
2namespace Webkul\Test\Ui\Component\Create\Form\Customer;
3 
4use Magento\Framework\Data\OptionSourceInterface;
5use Magento\Customer\Model\ResourceModel\Customer\CollectionFactory as CustomerCollectionFactory;
6use Magento\Framework\App\RequestInterface;
7 
8/**
9 * Options tree for "Categories" field
10 */
11class Options implements OptionSourceInterface
12{
13    /**
14     * @var \Magento\Customer\Model\ResourceModel\Customer\CollectionFactory
15     */
16    protected $customerCollectionFactory;
17 
18    /**
19     * @var RequestInterface
20     */
21    protected $request;
22 
23    /**
24     * @var array
25     */
26    protected $customerTree;
27 
28    /**
29     * @param CustomerCollectionFactory $customerCollectionFactory
30     * @param RequestInterface $request
31     */
32    public function __construct(
33        CustomerCollectionFactory $customerCollectionFactory,
34        RequestInterface $request
35    ) {
36        $this->customerCollectionFactory = $customerCollectionFactory;
37        $this->request = $request;
38    }
39 
40    /**
41     * {@inheritdoc}
42     */
43    public function toOptionArray()
44    {
45        return $this->getCustomerTree();
46    }
47 
48    /**
49     * Retrieve categories tree
50     *
51     * @return array
52     */
53    protected function getCustomerTree()
54    {
55        if ($this->customerTree === null) {
56            $collection = $this->customerCollectionFactory->create();
57 
58            $collection->addNameToSelect();
59 
60            foreach ($collection as $customer) {
61                $customerId = $customer->getEntityId();
62                if (!isset($customerById[$customerId])) {
63                    $customerById[$customerId] = [
64                        'value' => $customerId
65                    ];
66                }
67                $customerById[$customerId]['label'] = $customer->getName();
68            }
69            $this->customerTree = $customerById;
70        }
71        return $this->customerTree;
72    }
73}
74

1<field name="customer" component="Webkul_Test/js/components/select-customer" sortOrder="20" formElement="select">
2    <argument name="data" xsi:type="array">
3        <item name="config" xsi:type="array">
4            <item name="filterOptions" xsi:type="boolean">true</item>//to add filter in select-ui
5            <item name="multiple" xsi:type="boolean">false</item>//select multiple or not
6            <item name="showCheckbox" xsi:type="boolean">true</item>
7            <item name="disableLabel" xsi:type="boolean">true</item>
8        </item>
9    </argument>
10    <settings>
11        <required>true</required>
12        <validation>
13            <rule name="required-entry" xsi:type="boolean">true</rule>
14        </validation>
15        <elementTmpl>ui/grid/filters/elements/ui-select</elementTmpl>
16        <label translate="true">Select Customer</label>//label to Field
17        <dataScope>data.customer</dataScope>//To map
18        <componentType>field</componentType>
19        <listens>
20            <link name="${ $.namespace }.${ $.namespace }:responseData">setParsed</link>
21        </listens>
22    </settings>
23    <formElements>
24        <select>
25            <settings>
26                <options class="Webkul\Test\Ui\Component\Create\Form\Customer\Options"/>
27            </settings>
28        </select>
29    </formElements>
30</field>
31