How to add user-picker field for Jira custom plugin

I'm creating a custom plugin for Jira.I now have start date and end date fields.How can I add a field to select the user for which the report will be generated?

<atlassian-plugin key="${atlassian.plugin.key}" name="${project.name}" plugins-version="2"><plugin-info>    ...</plugin-info><report name="Creation Report" ...><description ...><resource ...><property><key>startDate</key><name>report.issuecreation.startdate</name><description>report.issuecreation.startdate.description</description><type>date</type></property><property><key>endDate</key><name>report.issuecreation.enddate</name><description>report.issuecreation.enddate.description</description><type>date</type></property><property><key>users</key><name>report.issuecreation.users</name><description>report.issuecreation.users.description</description><type>select</type> # i don't know            ???</property></report></atlassian-plugin>