Add `Connected` event to `ConnectionEvent` and `GattConnectionEvent`

[HaoboGu]

It seems like now ConnectionEvent and GattConnectionEvent lack an event that indicates the "logical" connected. PairingComplete is emitted only when there's a pairing procedure, aka the first connection. But for saved connections there's no event for "connected", which means that the security check is passed, now data can be exchanged.

[lulf]

I don't think I understand a need for this event, because you cannot get a Connection instance without it actually being connected from advertiser accept() or central connect(), which returns only when it is actually connected.

[HaoboGu]

yeah, so I quote it as "logical" connected. Because when the peripheral is connected to a bonded central, it connects successfully first(aka advertiser.accept returns Ok(Connection)) and then encrypts the connection using bond_information, but if the security check fails(for example, bonding information was cleared in the peripheral), then the connection will be dropped. From users perspective, the peripheral and central doesn't really connected to each other.

[lulf]

I forgot to reply to this. What I'm against is to emit the logical connected event for unencrypted connections, because it sort of leads to two things meaning the same thing. Maybe naming it something more specific related to pairing/bonding?

[HaoboGu]

Maybe we need a EncryptionEnabled event which can be emitted here?

[lulf]

Yeah, that feels more intuitive to me