Tracking Issue: Data Volume insights

[StephenWakely]

RFC

Requirements:

• Add the source field to the Event metadata to indicate the source the event has come from. #17577
• Update the Volume event metrics to take a JsonSize value. Use the compiler to ensure all metrics emitted use this. The EstimatedJsonEncodedSizeOf trait will be updated return a JsonSize. #17578
• Add the Service meaning. Update any sources that potentially create a service to point the meaning to the relevant field. #17579
• Introduce an event caching layer that caches registered events based on the tags sent to it. #17580
• Update the emitted events to accept the new tags - taking the telemetry configuration options into account. #17581
• Ensure meanings are attached to the events at runtime so that we can extract the service from the event. Closed by feat: track runtime schema definitions for log events #17692
• There is going to be a hit on performance with these changes. Add benchmark case with multiple services and sources to help us understand how much the impact will be.
• Ensure the Json size is the size after the event has been transformed but before encoding. Likely this will need the RequestBuilder to be restructured a little.
• Ensure all the sinks emit the Source and Service tags. All V2 sinks should already be covered, but need checking. Old style sinks will likely need work. Can we add this to the assert event compliance tests?