Expand appstatus godoc
Expand appstatus godoc

Add examples and reasoning.

Change-Id: If446d17653b0612dc3e7c17686eec7e7bdedb58e
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/2173299
Reviewed-by: smut <95deb7aa15d4c615299e47e7688551456568b1fb@google.com>
Commit-Queue: Nodir Turakulov <ef4933a197ef7b4b3f55f1bec4942aead3637a2a@chromium.org>

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go