add contact feature

[humorless]

Add contact button

• An "Add contact" button in the menu.
• Brings up a QR code.
• Properly encode the data inside QR code.
• Someone else can scan this QR code using their own camera, and then get connected.
• After connection, the other person shows up in a list of "connecions."

progress

• show QR code

• contact shows after scan the QR code and get the that http link

Use case:

I'm talking to a cool person at the bar, how do I keep in touch with you?

[humorless]

In my experiment, :cardinality/many seems to assure that the value of that attribute is unique.

Run the code below several time, and user/contacts is written only in the first time.

(let [result @(db/transact [{:db/id 17592186045495
                             :user/contacts 5}])]
  (clojure.pprint/pprint result))