Improvement: Extend serdeContextBase by operationName

[VladimirGorobetsWildix]

Here’s a clearer and more structured version of your description:

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I need to extend serdeContextBase in ServerGenerator.java.

When I make a request to my ssdk, I receive a ValidationException. I want to add metrics for this, but I can't determine which command was executed.

If you add operationName to serdeContextBase, I'll be able to access this information everywhere.

Example:

    @Override
    protected void writeDefaultOutputHeaders(GenerationContext context, OperationShape operation) {
        context.getWriter().write("'x-command-name': ctx.operationName,");
    }

    @Override
    protected void writeDefaultErrorHeaders(GenerationContext context, StructureShape error) {
        context.getWriter().write("'x-command-name': ctx.operationName,");
    }

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