Feature: Send Portal Instructions

[johnnyq]

When enabling portal login during add/edit contact add checkbox at the end to send portal instructions to contact along with a secure one time link of their creds.

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Almost complete - the "Send user email with login details" shows when editing an existing contact.

We just need the box to appear when adding a contact:

[wrongecho]

Also e943faecf0be76c514c8d764ad408c704269edb2

[wrongecho]

https://github.com/itflow-org/itflow/pull/735