String should be TKey in DapperStoreOptionsExtentions to use different ID type

[SZLMCL]

Hello,

I would like to use Guid ID type as ID of Users and Roles...

In the current extension method the 'string' type is hardcoded in more place (one example):

    public static void AddUserRolesTable<TUserRolesTable, TUserRole>(this DapperStoreOptions options)
        where TUserRolesTable : UserRolesTable<IdentityRole, string, TUserRole>
        where TUserRole : IdentityUserRole<string>, new() {
        options.AddUserRolesTable<TUserRolesTable, IdentityRole, string, TUserRole>();

I think the string type should be replaced with TKey.