AddAdminUser add an admin to given group.

AddUser add a user to given group.

ChangeUsernameOnGroups changes a username on groups.

CountGroups returns the total number of groups in db.

Delete deletes a group.

FindByName returns matching group by groupname.

GetGroups returns all user's groups.

GetUserGroupsOnlyName returns only groupname of user's groups.

InitDB creates default group if necessary.

Insert insert new group.

IsGroupnameExists return true if groupname exists, false otherwise.

IsUserAdmin return true if user is admin on this group.

ListGroups return all groups matching given criteria.

RemoveAdminUser remove an admin from a group.

RemoveUser remove a user from a group.

Update updates a group : name and description.