Document new WaitDone feature

[chrismetz09]

based on ligato/vpp-agent#1734

[chrismetz09]

Hacked text follow:

In some scenarios, you could have configuration updates that depend on a data plane event. Problems can arise if your agent expects a completed configuration update, while the underlying data plane is not fully configured. In other words, the configurator signals config update finished , but key-values are still PENDING. See Issues #1732 for details on this problem.

You can tell the configurator to wait until all key-value pairs are non-PENDING with the waitdone option. The configurator proto defines a wait_done boolean. If set to true, the configurator waits for all key values to reach non-PENDING state before signaling config update finished, or until the request times out. Note that config update and config delete support the waitdone option.

For more information on waitdone, see the following:

• Configurator proto
• configurator.go
• feat: Add support for waiting until config update is done #1734
• feat: Implement WaitDone for Delete in Configurator service #1756