Consider adding MQTT v5 properties to output of mosquito_sub

[manifest]

It seems reasonable to output MQTT v5 properties in the output of mosquito_sub. That may be hidden behind by -v, -d, and -F flags.

The current behavior

## Default
mosquitto_sub -V 5 -t 'foo'
bar

## Verbose
mosquitto_sub -v -V 5 -t 'foo'
foo bar

## JSON output of message parameters
mosquitto_sub -F "%j" -V 5 -t 'foo'
{
  "tst": 1568918942,
  "topic": "foo",
  "qos": 0,
  "retain": 0,
  "payloadlen": 3,
  "payload": "bar"
}

For

mosquitto_pub -V 5 -t 'foo' -m 'bar' -D publish user-property a b

Mosquitto version: 1.6.4
OS: macOS

[ralight]

Yes.

I'm not sure the best way to approach it though. Perhaps it could be restricted to the json output.

[manifest]

I'm not sure the best way to approach it though. Perhaps it could be restricted to the json output.

That will work for us.

[ralight]

This should now be working fully. Please give it a try on the develop branch. You can have it either in the JSON output using -F %j or -F %J, or using new format specifiers: -F %A %C %D %E %F %P %R %S.

[manifest]

That seems fine to me. Thanks.

[manifest]

Just a note about binaries: it may be a bit more useful (readable) to represent them as arrays of integers (in a range of 0 - 255). We always know which property has the binary type, so there won't be any confusion.

[manifest]

Payload is also a binary. It would be nice to attempt representing it as a string, at first. If not possible, to fall to the binary representation (array of integers).