Busy status support

[Rello]

nextcloud/files-clients#103

The client has a UI to set the user status. currently there are Away, Online, DoNotDisturb, Invisible.

The new status "Busy" is added on the server in a recent release. As this is not available in older releases, it is promoted via the server capabilities as 'supports_busy'.

The user status capabilities looks like this:

			'user_status' => [
				'enabled' => true,
				'restore' => true,
				'supports_emoji' => $this->emojiHelper->doesPlatformSupportEmoji(),
				'supports_busy' => true,
			],

Add the following feature:

• check for server capabilities as part of the existing capabilities check
• Add the ui depending on the capabiliites to select the new status
• the icon should be the same as away
• "Busy" should show up after "Away" in the UI
• update the clien to show the correct status when being set on the server