add owner role support (#1340)

This PR adds support to Owner roles.

The owner role has a similar access level as the admin, but it has the power to delete the account.

Besides that, the role has the following constraints:

- The role can only be transferred. So, only a user with the owner role can transfer the owner role to a new user
- It can't be assigned to users being invited
- It can't be assigned to service users

management/server/peer.go

@@ -214,7 +214,7 @@ func (am *DefaultAccountManager) GetPeers(accountID, userID string) ([]*Peer, er
 	peers := make([]*Peer, 0)
 	peersMap := make(map[string]*Peer)
 	for _, peer := range account.Peers {
-		if !user.IsAdmin() && user.Id != peer.UserID {
+		if !user.HasAdminPower() && user.Id != peer.UserID {
 			// only display peers that belong to the current user if the current user is not an admin
 			continue
 		}
@@ -862,7 +862,7 @@ func (am *DefaultAccountManager) GetPeer(accountID, peerID, userID string) (*Pee
 	}
 
 	// if admin or user owns this peer, return peer
-	if user.IsAdmin() || peer.UserID == userID {
+	if user.HasAdminPower() || peer.UserID == userID {
 		return peer, nil
 	}