Emit transaction.data inside contexts.trace.data

[bitsandfoxes]

Relates to getsentry/team-sdks#95
See getsentry/team-sdks#95 (comment) for more details.

Current Behavior

• We currently map extra to data in our SDK
• When serializing SentryTransaction, the extra data gets written to extra. The ITransactionTracer inherits from IHasExtra so this makes sense.
  

  sentry-dotnet/src/Sentry/SentryTransaction.cs

  Line 404 in 7024f37

  writer.WriteDictionaryIfNotEmpty("extra", _extra, logger);

Problem

The current inheritance structure prevents us from correctly mapping:

• Transaction data to contexts.trace.data
• Span data to span.data

Proposed Solution

Instead of modifying the inheritance structure for transactions and spans (which would be hacky), we should:

1. Add SetData methods to both TransactionTracer and SpanTracer
2. Keep existing SetExtra functionality
   • This allows users to quickly add contexts without creating a full context
   • Note: We do not support arbitrary key-value pairs on the context

Technical Details

• Transaction data should map to: contexts.trace.data
  • Implementation via ITraceContext so this gets written in the correct place automatically with
    

    sentry-dotnet/src/Sentry/SentryTransaction.cs

    Line 398 in 7024f37

    writer.WriteSerializableIfNotNull("contexts", _contexts.NullIfEmpty(), logger);

• Span data should map to: span.data

[bruno-garcia]

Span.Data should end up on on context.trace.data too:

sentry-dotnet/src/Sentry/SpanTracer.cs

Line 88 in 3f63cb6

public IReadOnlyDictionary<string, object?> Extra => _data;

So we might want to add an Obsolete on SetExtra if that was used to jsut make transaction and span "look alike"

[bruno-garcia]

Another thought, since we have:

sentry-dotnet/src/Sentry/SentryContexts.cs

Line 59 in 3f63cb6

public Trace Trace => _innerDictionary.GetOrCreate<Trace>(Trace.Type);

We could have Span.Data map to that property