Python Bug: Serialized _Chat Content_ types incompatible with .NET #9627

Describe the bug
Python and .NET content types are not cross compatible when serialized to JSON.

Repro #1

1. Serialize python history as JSON
2. Deserialize JSON in .NET

Repro #2

1. Serialize .NET history as JSON
2. Deserialize JSON in .python

Expected behavior
Content types are compatible across platforms

Screenshots

Content Type Compatibility.xlsx
dotnet-history.json
python-history.json

The yellow highlighted items are ones that might be easily addressed with case (upper/lower/snake) conversion (for example, using an ignore case option on deserialization) and also not writing null/empty values.

The pink highlighted items are more structural. Some might be easily addressed (don't write inner_content); while others may challenging to unwind

In addition:

• .NET utilizes HTML encoding for text content.
• Meta-data keys differ across platform based on the OpenAI SDK

Additional context
This has compatibility has long been identified as desired, but not directly analyzed or addressed. Performed analysis for critical types as part of agent framework serialization feature and capturing here:

• KernelContent
• ChatMessageContent
• TextContent
• FunctionCallContent
• FunctionResultContent

Other content types include:

• AnnotationContent
• AudioContent
• BinaryContent
• FileReferenceContent
• ImageContent