Allow an optional encoding of the timestamp in the CBOR message

[aentinger]

In order to enable the encoding of the timestamp you can've got to call encodeTimestamp() when adding the property to the cloud within thing_properties.h.

ArduinoCloud.addProperty(seconds, Permission::Read).publishOnDemand().encodeTimestamp();

In order to set the timestamp of the property you call

seconds_timestamp = seconds; /* = 45 in below CBOR */
ArduinoCloud.setTimestamp("seconds", seconds_timestamp);

This is the resulting CBOR

[{0: "seconds", 2: 45, 6: 45}]

@zmoog @manchoz 👋

[codecov-commenter]

Codecov Report

Merging #137 into master will decrease coverage by 0.60%.
The diff coverage is 78.37%.

@@            Coverage Diff             @@
##           master     #137      +/-   ##
==========================================
- Coverage   96.15%   95.55%   -0.61%     
==========================================
  Files          30       29       -1     
  Lines         988      989       +1     
==========================================
- Hits          950      945       -5     
- Misses         38       44       +6     

Impacted Files	Coverage Δ
src/property/Property.h	90.47% <ø> (-9.53%)	⬇️
src/property/Property.cpp	86.16% <36.36%> (-3.17%)	⬇️
src/property/PropertyContainer.cpp	89.58% <95.45%> (+2.31%)	⬆️
src/cbor/ArduinoCloudThing.cpp	96.07% <100.00%> (ø)

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[aentinger]

Successfully tested on PROD with

• Nano 33 IoT ✔️

[github-actions]

Memory usage change @4959e2b08c24e22de72a9ee5ce26f37de7a48c3e

FQBN	Flash Usage	RAM For Global Variables
arduino:samd:mkr1000	🔺 +32	💚 -8
arduino:samd:mkrgsm1400	🔺 +32	💚 -8
arduino:samd:mkrnb1500	🔺 +32	💚 -8
arduino:samd:mkrwan1300	🔺 +56	💚 -12
arduino:samd:mkrwifi1010	🔺 +32	💚 -8
arduino:samd:nano_33_iot	🔺 +32	💚 -8
esp8266:esp8266:huzzah	🔺 +16	💚 -8