[BUG] FlatteningSerializer not work correctly for Map/List with final modifier

[weidongxu-microsoft]

Describe the bug
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It breaks the "dot" in Map key, result in e.g. {"operation":"Replace","properties":{"tags":{"tag":{"1":"value.1"}}}}

Sample case #20149

Code on https://github.com/Azure/azure-sdk-for-java/blob/master/sdk/core/azure-core/src/main/java/com/azure/core/util/serializer/FlatteningSerializer.java#L106-L122

It happens to track1, reported by Databricks. Checked on track2, still reproducible (though it is now limited to classes annotated with @JsonFlatten).

I am not able to find good solution for this, as the Map or List might not even be modifiable.

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To Reproduce
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Sample case #20149

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Sample case #20149

Expected behavior
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Setup (please complete the following information):

• OS: [e.g. iOS]
• IDE : [e.g. IntelliJ]
• Version of the Library used: azure-core 1.14.1

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[weidongxu-microsoft]

@anuchandy @jianghaolu for awareness.

[weidongxu-microsoft]

Another case found:

@JsonFlatten ClassA
-- propertyA: final ClassB
---- propertyB: Map<>

The escaping of Map get interrupted by the "final" ClassB via https://github.com/Azure/azure-sdk-for-java/blob/azure-core_1.6.0/sdk/core/azure-core/src/main/java/com/azure/core/util/serializer/FlatteningSerializer.java#L121-L123

It could be solved by the "shallow" JsonFlatten (as it will not touch ClassB hence no need to escape propertyB) .However I am not sure what might be the impact of changing behavior from "deep" to "shallow".

[samvaity]

Fixed with ##22591 to allow flattening of static and final variables.