nix: configure sharefs via fileSystems

Turns out this did not work because in the vm test harness, virtualisation.fileSystems completely and silently overrides fileSystems, causing its contents to not even be evaluated anymore. This is not documented as far as I can tell, and is not obvious by any stretch of the imagination. The current hack is cargo culted from nix-community/impermanence and hopefully lasts until this project fully replaces nix.

Signed-off-by: Ophestra <cat@gensokyo.uk>

options.md

@@ -809,6 +809,96 @@ package
 
 
 
+## environment\.hakurei\.sharefs\.package
+
+
+
+The sharefs package to use\.
+
+
+
+*Type:*
+package
+
+
+
+*Default:*
+` <derivation sharefs> `
+
+
+
+## environment\.hakurei\.sharefs\.group
+
+
+
+Name of the group to run the sharefs daemon as\.
+
+
+
+*Type:*
+string
+
+
+
+*Default:*
+` "sharefs" `
+
+
+
+## environment\.hakurei\.sharefs\.name
+
+
+
+Host path to mount sharefs on\.
+
+
+
+*Type:*
+string
+
+
+
+*Default:*
+` "/sdcard" `
+
+
+
+## environment\.hakurei\.sharefs\.source
+
+
+
+Writable backing directory\. Setting this to null disables sharefs\.
+
+
+
+*Type:*
+null or string
+
+
+
+*Default:*
+` null `
+
+
+
+## environment\.hakurei\.sharefs\.user
+
+
+
+Name of the user to run the sharefs daemon as\.
+
+
+
+*Type:*
+string
+
+
+
+*Default:*
+` "sharefs" `
+
+
+
 ## environment\.hakurei\.shell