Add redirect uri options to workshop

[Velua]

When handling valid redirect urls, we need to support either a full URL or simply a path on the app.

• Update the accounts app to support parsing & checking if the query params are valid.
• Update the workshop app to support storing this metadata.

Examples

Path only

&redirect=/invite-response -> http://invitingApp.psibase.127.0.0.1.sslip.io:8080/invite-response

Full domain

&redirect=https://api.monstereos.com/invite-response -> https://api.monstereos.com/invite-response

If path array is empty, all paths are wildcarded.
This behavior does not apply for full urls.