Set time zone from HK metadata in FHIR resources

[vishnuravi]

Set time zone from HK metadata in FHIR resources

♻️ Current situation & Problem

The HealthKitOnFHIR library currently assumes that HealthKit samples were created in the current time zone of the device at the time of mapping and applies the corresponding UTC offset. While this is true for most situations, it is possible that older HealthKit data may be mapped using the library that was created while the user was in a different time zone.

For example, if a sample was originally created by HealthKit in San Francisco on December 1st, 2024 at 9:00am (-08:00), but then mapped by HealthKitOnFHIR later on in New York, the timestamp would read 2024-12-01T12:00:00-05:00. While technically these are the same point in time, they are offset differently.

The information regarding the original timezone of the sample may be stored by HealthKit in the object's metadata via HKMetadataKeyTimeZone, if this was written by the original application or device that created the data, and we should use it to apply the appropriate offset.

⚙️ Release Notes

• If a time zone has been defined in HKMetadataKeyTimeZone, it is set when serializing HealthKit samples.

✅ Testing

Unit tests have been updated to test that the appropriate offset is applied for multiple time zones specified via metadata and test that the offset of the current time zone is applied if none is specified.

Code of Conduct & Contributing Guidelines

By submitting creating this pull request, you agree to follow our Code of Conduct and Contributing Guidelines:

• I agree to follow the Code of Conduct and Contributing Guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.92%. Comparing base (a1a7125) to head (e20e9ae).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
+ Coverage   92.71%   92.92%   +0.21%     
==========================================
  Files          23       24       +1     
  Lines        1097     1115      +18     
==========================================
+ Hits         1017     1036      +19     
+ Misses         80       79       -1     

Files with missing lines	Coverage Δ
.../HealthKit Extensions/HKSample+ResourceProxy.swift	97.44% <100.00%> (+0.30%)	⬆️
...nFHIR/HealthKit Extensions/HKSample+TimeZone.swift	100.00% <100.00%> (ø)
...HIR/Observation Extensions/Observation+Dates.swift	100.00% <100.00%> (+6.67%)	⬆️

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[PSchmiedmayer]

Looks great; thank you for the quick feature addition! 👍