Add support for Temporal objects

[connor-baer]

Purpose

SumUp has decided to adopt Temporal, the upcoming modern date/time API for the ECMAScript language, to handle dates and times in web applications. Replacing heavy date-time libraries currently in use will improve page load performance, while converging on a single standardized API will ensure interoperability and consistency between applications.

The proposal for Temporal has been making its way through the ECMAScript standardization process since 2017. It has reached stage 3 (recommended for implementation) but hasn't been implemented and unflagged in any browsers yet.

Until the Temporal API is widely supported, we will use the temporal-polyfill package, a well-tested, spec-compliant polyfill. We can guard against incompatibilities with future spec changes by importing the polyfill locally, not globally, effectively treating it as a regular dependency, which enables us to safely adjust our code (if necessary) when we upgrade to the latest/final polyfill/spec version.

Approach and changes

• Add temporal-polyfill as a required peer dependency. I chose a strict dependency range (0.2.x) since there might be breaking changes between minor versions. We'll need to test new versions for compatibility and adjust the allowed version range accordingly.
• Use the Intl.DateTimeFormat constructor from temporal-polyfill which has been patched with support for Temporal objects.

Definition of done

• Development completed
• Reviewers assigned
• Unit and integration tests
• Meets minimum browser support
• Meets accessibility requirements

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.27%. Comparing base (6b8dc64) to head (d9b725e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #250      +/-   ##
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+ Coverage   93.26%   93.27%   +0.01%     
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  Files          15       15              
  Lines         668      669       +1     
  Branches       84       84              
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+ Hits          623      624       +1     
  Misses         43       43              
  Partials        2        2              

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[changeset-bot]

🦋 Changeset detected

Latest commit: e3211c9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sumup/intl	Major

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