• Fix vmq_webhooks issue where MQTTv5 hooks where not configurable in the
  vernemq.conf file.
• Support shared subscriptions in vmq_bridge.
• Fix bug in Prometheus output (#923).
• Fix max_message_rate to include MQTTv5 sessions.
• Support new throttle modifier for the auth_on_publish and
  auth_on_publish_m5 hooks which will throttle the publishing client by
  waiting for a given number of milliseconds before reading new data from the
  client socket. Note, backpressure is not supported for websocket
  connections. This feature was kindly sponsored by Arduino SA
  (https://www.arduino.cc/).
• Fix issue with long-running vmq-admin commands (#644).
• Added a new HTTP module vmq_health_http exposing a /health endpoint that
  returns 200 when VerneMQ is accepting connections and joined the cluster
  (for clustered setups) or returns 503 in case any of the two conditions
  are not met (#889).
• Fix issue where a QoS2 message would be republished if a client would resend
  the PUBLISH packet with the same message id within a non-finished QoS2 flow
  (#944).
• Make VerneMQ build on FreeBSD (11.2-RELEASE) with gmake rel.
• Fix issue with blocking socket commands in inter-node communication.
• Improve error messages when parsing invalid CONNECT packets.
• Log IP and port information on authentication failures to make it easy to
  block the client with tools like Fail2ban (#931).
• Fix issue which would crash the session if a client would resend a (valid)
  pubrec during a Qos2 flow (#926).
• Fix vmq_diversity error message if invalid or unknown modifiers are returned
  from a lua hook implementation.
• Fix issue preventing MQTT 5.0 properties from being modifiable in
  auth_on_publish_m5 (#964).
• Fix issue which causes a crash if not enough data is available while parsing
  the CONNECT frame in vmq_mqtt_pre_init (#950, #962).
• Fix issue which could cause vmq-admin session show to crash when using
  --limit=X to limit the number of returned results (#902).
• Handle edge case in the websocket implementation which could cause warninigs
  when the session was terminating.
• Expose vernemq_dev_api:disconnect_by_subscriber_id/2 in lua
  vmq_api.disconnect_by_subscriber_id/2, an example looks like:
  vmq_api.disconnect_by_subscriber_id({mountpoint = "", client_id = "client-id"}, {do_cleanup = true}).
• Improve vmq_webhooks errors so the error from the endpoint is shown as the
  error reason where relevant.
• Optimization: optimize away read operation during client registration by
  reusing already available data.
• Enable plugins to expose metrics via the available metric providers.
• Add histogram metric type.
• Fix incorrect debug log message in QoS 2 flow.
• Expose bridge metric for messages dropped in case the outgoing queue is full.
• Log (debug level) when a LWT is suppressed on session takeover.
• Optimize subscribe operation by refactoring away one read from the metadata
  store.
• Add protection mechanism for the plumtree metadata store from subscription
  floods by dropping and not acknowledging i_have messages when the mailbox
  size grows above a certain threshold. This threshold is configurable via the
  plumtree.drop_i_have_threshold hidden option. The default is 1000000. This
  work was kindly contributed by ADB (https://www.adbglobal.com).
• Add new vmq-admin retain commands to inspect the retained message store.
• Support for different MySQL password hashing methods in vmq_diversity,
  ensuring compatibility with MySQL 8.0.11+. The method is configurable via the
  vmq_diversity.mysql.password_hash_method option which allows:
  password (default for compatibility), md5, sha1 or sha256.
• Fix the HTTP /status.json endpoint to have a valid JSON output (#786).
• Fix bug where internal application plugins where shown as normal plugins.
• Fix crash in bridge when calling vmq-admin session show by fixing the
  vmq_ql row initializer to handle plugin sessions (the bridge starts a local
  plugin session).
• Add improvements to VerneMQ status page to have nicer UI and be readable on smaller devices.
• Upgraded dependency sext to 1.5.0 (required for better OSX compilation).
• Do not accept new client connections while the broker is shutting down as this
  could cause errors to be reported in the log (#1004).
• Fix vmq_diversity PostgreSQL reconnect issue (#1008).
• Fix vmq_webhooks so peer port is not considered when caching the
  auth_on_register to avoid cache misses.
• Multiple bug fixes and improvements in vmq_swc.
• Add the vmq_swc metadata plugin (using the already existing LevelDB backend) to
  the default VerneMQ release. To use vmq_swc instead of vmq_plumtree set
  metadata_plugin = vmq_swc in vernemq.conf. vmq_swc is still in Beta.
• Add missing increments of the mqtt_connack_sent metric for CONNACK
  success(0) for MQTT 3.1.1.
• Handle edge case with unknown task completion messages in vmq_reg_sync after
  a restart.
• Fix bug which could cause a queue cleanup to block indefinitely and cause the
  vmq_in_order_delivery_SUITE tests to fail.
• Add a new metric (queue_initialized_from_storage) to better monitor queue
  initialization process after a node restart.
• Fix edge case where an extra queue process could be started when metadata
  events arrive late. Now local queue processes are only started when triggered
  via a new local MQTT session.
• Reimplement dead queue repair mechanism.
• Add feature to reauthorize existing client subscriptions by reapplying current auth_on_subscribe
  and auth_on_subscribe_m5 hooks. This feature is exposed as a developer API in vernemq_dev, via
  the vmq-admin session reauthorize CLI command, and as a API for vmq_diversity Lua scripts. This
  work was kindly sponsored by AppModule AG (http://www.appmodule.net).
• Improve planned cluster leave queue migration speed significantly (#766).
• Start metrics server before setting up queues to ensure queue metric counts
  are correct when restarting VerneMQ.
• Let Travis CI build the VerneMQ release packages.
• Add new metric system_process_count which is a gauge representing the
  current number of Erlang processes.
• Add queue_started_at and session_started_at information to the vmq-admin session show command. Times are POSIX time in milliseconds and local to the
  node where the session or queue was started.