Support Span Links in Assertions

[jorgeepc]

Context: The OTel specification defines Span Links as a way to associate one span with one or more spans, implying a causal relationship. They are an optional feature but serve as a good way to associate trace spans with one another. Span Links are also considered a common practice when working with asynchronous operations like tracing queues.

Objective: The goal of this ticket is to support Span Links in the Tracetest Assertion Engine.

Key Goals:

• Tracetest should be capable of ingesting and extracting trace data generated by OTel instrumentation that is using Span Links. This involves parsing the trace data to identify span relationships and extracting the necessary information to create Span Links.
• The assertion engine must support verification of Span Links within the trace data. This includes defining assertions that validate the presence or absence of Span Links between different spans within a trace.
• Offer visualization capabilities to help users understand the relationships between spans and the presence of Span Links within traces.
• The Test Specs UI must support the creation of Span Links assertions.
• Documentation should be updated with instructions for verifying Span Links in OpenTelemetry traces.