Element-android: QR-codes for faster contact sharing

[totikom]

The problem

When I want to share a contact (my or someone else's) with the person I've met face to face, I need to spell (or show) my full Matrix ID, which is not very convenient. Otherwise, I can send matrix.to link with some external communication method, which is also not very fast.

Proposed solution

On the "profile page" add "show QR-code" button, which will create QR-code with matrix.to link.

It will allow users to quickly exchange Matrix IDs, which seems quite usefull.

[notramo]

It should also do the verification in the same QR code.

[totikom]

I don't think that it is possible due to the verification protocol. It requires exchange of information in both directions.

[bahur142]

This will be very useful feature to add someone in the contact list when face-to-face.
And then adding new contacts can happen like that:

[ralaud]

Maybe duplicate of Related to #312

[totikom]

Related but not a duplicate, as I propose _arbitrary contact_ sharing, not just your own.
For example, then I want to recommend one of my fellows to another, I can quickly show him/her the code. Apart from verification process there is no difference between sharing my and someone else's ID.

[notramo]

@totikom It is possible, although not with the current methods. E.g. the QR code contains a shared secret, and the scanner salts his own key with the secret.