code: public <T> T doWithUser(final String user, final SpecificUserAction<T> action) {
          return userManager.executeWithTxUser(user, action);
      }
docs: Execute logic with specific user. Changes user only inside transaction.
  Used, for example, to force security checks.
  <p>
  See {@link ru.vyarus.guice.persist.orient.db.user.UserManager#executeWithTxUser(
  String, ru.vyarus.guice.persist.orient.db.user.SpecificUserAction)}.
  <p>
  Use {@link ru.vyarus.guice.persist.orient.db.user.UserManager} directly to change user for
  multiple transactions.
  <p>
  LIMITATION: current user must have read right on users table.
  
  @param user   user login
  @param action action to execute under user
  @param <T>    type of returned result (may be Void)
  @return action result (may be null)