Fix: date custom converter to serialize and deserialize ISO 8601 date and time

[KoditkarVedant]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #425 & #429

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

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• Test A
• Test B

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Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

Src/Notion.Client/Models/PropertyValue/DateCustomConverter.cs:45

• [nitpick] Consider using CultureInfo.InvariantCulture when formatting the date (e.g., value.Start.Value.ToString(startFormat, CultureInfo.InvariantCulture)) to ensure consistent serialization across different locales.

writer.WriteValue(value.Start.Value.ToString(startFormat));

Src/Notion.Client/Models/PropertyValue/DateCustomConverter.cs:52

• [nitpick] Consider using CultureInfo.InvariantCulture when formatting the 'end' date (e.g., value.End.Value.ToString(endFormat, CultureInfo.InvariantCulture)) for consistent behavior regardless of system culture.

writer.WriteValue(value.End.Value.ToString(endFormat));

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

Src/Notion.Client/Models/PropertyValue/DatePropertyValue.cs:51

• Verify that excluding the IncludeTime property from JSON serialization is intentional, as the custom converter handles the time formatting.

[JsonIgnore]

[Copilot]

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.