YARP timeout docs should mention HttpClient `ActivityTimeout`

[gumbarros]

In the current docs about YARP Timeouts, there’s no mention of ActivityTimeout.

This is confusing because ActivityTimeout has a default of 100 seconds, which silently overrides route-level Timeout values longer than that.

For example:

• If you configure a route Timeout of 300 seconds, it will be ignored because the request is still canceled after the default ActivityTimeout of 100s.
• But if you configure a route Timeout of 1 second, it does take effect.

This behavior can make debugging really painful, since developers may think their configured Timeout is being honored when in reality it’s capped by ActivityTimeout, it drove us insane this morning :)

The docs should explicitly call out the interaction between Timeout and ActivityTimeout, and clarify which one takes precedence in different scenarios.

[MihaZupan]

Thanks for raising the issue, yes, improving docs here makes sense.

The behavior is that both will apply.
ActivityTimeout is just refreshing its timer if something's still happening with the request. If the request is seemingly idle, then effectively whichever one is lower applies.

For debugging, note that the regular Timeouts feature does not apply when you have a debugger attached.
ActivityTimeout makes no such distinction though, it's always set.