migrate clanmodules/{user,root}-password to clanServices/users

Move the functionality of both modules into a new clanService.
root-password was previously just a special case of user-password. This
migrates it into a deduplicated clan service and adds checks

clanModules/root-password/roles/default.nix

@@ -36,7 +36,7 @@
       if [[ -n "''${prompt_value-}" ]]; then
         echo "$prompt_value" | tr -d "\n" > "$out"/password
       else
-        xkcdpass --numwords 3 --delimiter - --count 1 | tr -d "\n" > "$out"/password
+        xkcdpass --numwords 4 --delimiter - --count 1 | tr -d "\n" > "$out"/password
       fi
       mkpasswd -s -m sha-512 < "$out"/password | tr -d "\n" > "$out"/password-hash
     '';