docs: document multi-dimensional array support and MaxJsonDepth limit

Adds a Notes section to the JSON extension README explaining that multi-dimensional (nested) arrays are now supported on write (GeoJSON LineString/Polygon/MultiPolygon) and that JSON serialization enforces a maximum combined object + array nesting depth of 64 to guard against stack overflow on pathological input. Adds a cross-reference from the SQL Server extension README since JsonFields nested writes go through the same serializer.

Author: philnach

Extensions/Json/README.md

@@ -43,3 +43,15 @@ Additionally, an optional `ItemProgressFrequency` parameter (`1000` by default)
     "ItemProgressFrequency": 1000
 }
 ```
+
+## Notes
+
+### Multi-dimensional arrays
+
+Multi-dimensional (nested) arrays are supported on write. This includes GeoJSON geometries such as `LineString` (2-D), `Polygon` (3-D), and `MultiPolygon` (4-D) `coordinates`. Documents that previously emitted `"System.Collections.Generic.List``1[System.Object]"` placeholders for these shapes now serialize correctly.
+
+### Maximum nesting depth
+
+To guard against pathological or recursively nested input (which would otherwise stack-overflow the host process), JSON serialization enforces a **maximum combined object + array nesting depth of 64**. Documents that exceed this limit are rejected with an `InvalidOperationException` whose message contains the phrase `nesting depth`.
+
+This limit is well above any realistic document — GeoJSON `MultiPolygon` reaches depth 5, and typical nested business documents are under depth 10 — but if you hit it, it almost always indicates a corrupt or self-referential source document.

Extensions/SqlServer/README.md

@@ -10,6 +10,8 @@ Source and sink settings both require a `ConnectionString` parameter.
 
 If surfacing data as JSON, the `JsonFields` parameter can be used to specify which fields should be treated as JSON strings. This is useful for building nested sets of data that should be handled as a nested object downstream.
 
+> **Note**: Nested objects written into a SQL column as a JSON string go through the shared JSON serializer and are subject to a **maximum combined object + array nesting depth of 64**. Sources exceeding this limit will fail with an `InvalidOperationException`. See the [JSON extension notes](../Json/README.md#notes) for details.
+
 ### Source
 
 Source settings also require either a `QueryText` or `FilePath` parameter with the SQL statement that defines the data to select.