Fix socket not reconnecting

[nduitz]

This handles error when the server closes connections.
The second commit implements a check for a open connection but it is not very resilient yet.
If the reconnect fails, the notification get's lost, either there needs to be some recovery mechanism or the response handler needs to be called.

#299

[nduitz]

Converted this to draft for now, I am still evaluating what else can be done so notifications won't get lost

[nduitz]

This got way bigger then expected but I think this is pretty solid now.
Would be glad if this got reviewed :)

This now handles mint errors while trying to push/reconnect to the different services.
If the push does not work, instead of throwing it away it get's requeued as a retry.
The number of retries can be configured, they use exponential backoffs between each retry (maybe should be configuriable too?)

I extracted a bit of adapter logic that applies to both apns + fcm to a helper. the ADM adapter does not use very much of it because it has a different behaviour