In JIRA you cannot invite via link. Only by email.
https://confluence.atlassian.com/display/JIRA/Managing+Users#ManagingUsers-Invitingusers
In Confluence though you can invite via link.
https://confluence.atlassian.com/display/DOC/Adding+and+Inviting+Users
When you create a JIRA user, there is an option to invite a user. Not really a public link though.
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