fix: CalDateTime CTOR using ISO 8601 UTC string resolves to UTC

[axunonb]

Throws for controversion of ISO 8601 UTC string, while timezone ID is not UTC

chore: ExcludeFromCodeCoverage for private constructor
chore: Remove unused method TruncateTimeToSeconds

Resolves #831

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❌ Your project status has failed because the head coverage (68%) is below the target coverage (80%). You can increase the head coverage or adjust the target coverage.

@@         Coverage Diff         @@
##           main   #833   +/-   ##
===================================
  Coverage    68%    68%           
===================================
  Files       106    106           
  Lines      4217   4214    -3     
  Branches    942    943    +1     
===================================
+ Hits       2850   2851    +1     
+ Misses     1039   1035    -4     
  Partials    328    328           

Files with missing lines	Coverage Δ
Ical.Net/DataTypes/CalDateTime.cs	90% <100%> (+2%)	⬆️

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[NRG-Drink]

CopyFrom is used only once and it will set _tzId regardless of the time.
I suggest to delete CopyFrom and use Initialize.

Suggested change

	CopyFrom(serializer.Deserialize(new StringReader(value)) as CalDateTime
	?? throw new InvalidOperationException($"$Failure for deserializing value '{value}'"));
	?? throw new InvalidOperationException($"$Failure when deserializing value '{value}'"));
	// The string may contain a date only, meaning that the tzId should be ignored.
	_tzId = HasTime ? tzId : null;
	_tzId ??= HasTime ? tzId : null;
	var dt = serializer.Deserialize(new StringReader(value)) as CalDateTime
	?? throw new InvalidOperationException($"$Failure when deserializing value '{value}'");
	Initialize(dt._dateOnly, dt._timeOnly, dt._tzId);

[axunonb]

Good catch, CopyFrom is redundant.
Initializing should read

Initialize(dt._dateOnly, dt._timeOnly, dt.IsUtc ? UtcTzId : tzId);

to reflect that UTC may be set from the deserialized string (appended 'Z') or from the tzId argument. This correction is actually the aim of the PR.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[axunonb]

@NRG-Drink Thanks for the helpful review