Server-Timing: allow `desc` field, make `dur` optional

[swissspidy]

Feature Description

The duration field is not mandatory for Server-Timing.

And description is very useful to provide more details.

You could actually also only serve a description, e.g. pageType;desc="index"

IMHO this should be supported by this API to make it more flexible.

[anandraj346]

Hi @swissspidy,

Could you please elaborate more about this issue

[swissspidy]

As per https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing the duration value is optional, and a description field is supported.

The PL plugin has a simple API to add Server-Timing headers where we would need to make this possible.