[7.11.24] Create form for contacts

[MizukiTemma]

Motivation

We are introducing a new feature "contact information". A form is needed for it.

Proposed Solution

Implement a form to create a new contact and to edit an existing one.

❓ Make it sure at least one of E-mail address, telephone number or website is given. 💡 Reuse venue_box.html for the step of selecting/creating a POI. 💡 Reuse _related_contents_table.html to show where the contact is embedded.

Alternatives

None. We do it.

User Story

Additional Context

Wait for #2952

Design Requirements

See the design here ⚠️ There are two versions in the link above. New Version 30.07 is the one we have to implement.