Refresh capabilities and signaling settings on `X-Nextcloud-Talk-Hash` header change

[nickvergessen]

Priority raises with #851

The requests for:

• /ocs/v2.php/apps/spreed/api/v1/room
• /ocs/v2.php/apps/spreed/api/v2/room
• /ocs/v2.php/apps/spreed/api/v1/room/{token}
• /ocs/v2.php/apps/spreed/api/v2/room/{token}

have a new X-Nextcloud-Talk-Hash header which contains a sha1 over some of the most important talk configs that affect communication and connections.
When you receive a different value on subsequent requests, the capabilities and the signaling settings should be refreshed asap.

See nextcloud/spreed@44131a8 for doc changes