Modify the Application: How?

Nobody has claimed this yet.

https://linkerd.io/2/tasks/distributed-tracing/ "Modify the Application" doesn't give details about how the application should be modified and why:

* Some tracing header must be passed on to outgoing requests. Which?
* In addition, some headers might be added to see how much time is spent in the application itself.
* However, that should be optional, correct? But the code uses the collector i.e. the application does report its time spans. The documentation should state that this is optional, if it is.
* It should be explained how the time spans are reported. Which headers? Is there some standard?

Background: I am trying to do the same with a Spring Sleuth based application and find it hard to understand how this can be done.

Start with the linked distributed-tracing task, focusing on the “Modify the Application” section and the Spring Sleuth context described here. Determine which tracing headers applications must forward, how application spans are reported, and whether reporting them is optional; document those details and their rationale in the task.

Written by the indexing model from the issue text.