* Add feature validation.

* Update ReleaseNotes.md

* Add validators or subscribe and unsubscribe.

* Add feature validation for disconnect.

* Fix build errors.

* Fix build errors
Co-authored-by: NHansM <HansM2013@gmx.de>

1546 possible bug in server repeatedly sending the same message to client subscribed with cleansession=false (#1569)

1552 mqttnetservermqttclientsessionsmanager subscribersessions is not proper removed on special case (#1562)

fix cross access to async events.

commit 469caf65
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sun Jul 31 10:55:40 2022 +0200

    Fix build errors.

commit 42402fba
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sun Jul 31 10:22:23 2022 +0200

    Allow interception of injected application messages.

commit a0dc8ab0
Author: William Lee <31092948+william19821101@users.noreply.github.com>
Date:   Sun Jul 31 15:50:14 2022 +0800

    Update Server_Simple_Samples.cs (#1474)

    Change e.UserName to e.Username

commit 353c9671a04a273798b0b3775be5f0764bfd7edf
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 23 15:33:01 2022 +0200

    Remove usage of obsolete stuff.

commit 1f3c35685c7a65453c37a37e8c54a2ca4305ff6d
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 23 15:30:54 2022 +0200

    Update ValidatingConnectionEventArgs.cs

commit a5e1b8938974b5b57e95ec41d74634ca130a8ad5
Merge: 8878efee 11249d00
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 23 15:30:30 2022 +0200

    Merge branch 'master' into 1125-expose-http-context-in-validateconnectionasync

commit 8878efee0da3c67d90bb7fb6946453f62329cd8e
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 23 15:30:03 2022 +0200

    Expose channel adapter when validating connections.

Squashed commit of the following: 487-any-way-to-generate-events-on-receipt-of-puback-or-pubrec-packets

commit 3f2f8d4b0a31b20734eca3fff86c43bd1ac3e3ad
Merge: 34babbf2 d71ff3d6
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 23 11:06:22 2022 +0200

    Merge branch 'master' into 487-any-way-to-generate-events-on-receipt-of-puback-or-pubrec-packets

commit 34babbf2714b742bc4f3802804a1a07159d38e22
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Mon Jul 11 22:56:01 2022 +0200

    Fix typo.

commit add6277458f528fc03bf4a1ba228a55c5a8d1a80
Author: Christian <6939810+chkr1011@users.noreply.github.com>
Date:   Sat Jul 2 12:50:13 2022 +0200

    Add new event for client acknowledges.