Add a way to set/update/delete OpenVPN client credentials from reForis. ## UI Based on the discussion, I would propose something similar to how we are handling DHCP static leases. I.e. something like following wireframes: <details><summary>Click to expand</summary>  With following modal:  </details> The same modal could be also used for adding new VPN client configuration, but I am not sure how to make the UI of "upload config and optionally set the client credentials". Feel free to change the design to be aligned with reForis style ;-) ## JSON messages Changes in request sent from reforis. ### Adding new client #### Before ``` { "config": {"type": "string"} } ``` #### New ```json { "config": {"type": "string"}, "credentials": { <-- this is optional attribute "username": {"type": "string"}, "password": {"type": "string"} } } ``` ### Set/Update client #### Before ```json { "id": {"$ref": "#/definitions/client_id"}, "enabled": {"type": "boolean"} } ``` #### New ```json { "id": {"$ref": "#/definitions/client_id"}, "enabled": "type": "boolean"}, "credentials": { <-- this is optional attribute "username": {"type": "string"}, "password": {"type": "string"} } } ``` --- Depends on: turris/foris-controller/foris-controller-openvpn_client-module#5