feat: Support json-mapped external type properties on Coalesce entities

[Copilot]

• Guard JsonCollection/ComplexCollection behind #if NET10_0_OR_GREATER
• Fix TypeScript test type errors (new WeatherData(...), null assertion)
• Guard C# test cases with #if NET10_0_OR_GREATER
• Add "JSON-mapped Complex Types" section to docs/modeling/model-components/properties.md
• Add 6.3 entry to CHANGELOG.md

Original prompt

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This section details on the original issue you should resolve

<issue_title>Explore complex json db-mapped entity fields</issue_title>
<issue_description>We already support json-mapped primitive collections, which get automatically mapped to json in the DB by EF with no special configuration. Explore what it would take to expand this to more complex scenarios (are there C# annotations for these?)

• Json-mapped object on entity
• Json-mapped collection of objects on entity</issue_description>

Comments on the Issue (you are @copilot in this section)

@ascott18 https://github.com/dotnet/efcore/issues/31252 @ascott18 ComplexTypeAttribute + [Column(TypeName = "json")]??? Will EF pick that up? @ascott18 Note: The "Property is non-scalar" logic in PropertySecurityInfo is one of the obstacles that will need to be adjusted to make this work. It seems that the comment in that code doesn't actually describe what the code is doing.

The EF configuration is .ComplexCollection(a => a.MyJsonCollection, cb => cb.ToJson()) or .ComplexProperty(a => a.Characteristics, cb => cb.ToJson()). I don't think we really need a special Coalesce attribute to pick this up. Extend the existing logic with hasWatcherFlag in viewmodel.ts for primitive collections to make this work with dirty checking.</comment_new>

• Fixes Explore complex json db-mapped entity fields #477

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[ascott18]

@copilot add/update documentation and update the changelog. This is now version 6.3 instead of 6.2.3.

[Copilot]

@copilot add/update documentation and update the changelog. This is now version 6.3 instead of 6.2.3.

Done in 23e9094. Added a "JSON-mapped Complex Types" section to docs/modeling/model-components/properties.md and added a 6.3 entry to CHANGELOG.md.