feat: add metrics for request length and response length

[matsumana]

Hi,
I would like to add the new metrics for Request length and Response length.

Motivation:
If an API handles a large JSON in request or response, the latency might get worse.
So I would like to monitor them.

[matsumana]

@joao-fontenele Could you take a look this PR?

[joao-fontenele]

Hello @matsumana

These are nice to have metrics, The only problem I see with this is making collecting it mandatory. If you make these changes optional, It would be good to merge

[matsumana]

Thank you for reviewing.
I have updated.

[matsumana]

@joao-fontenele Could you take a look this again?

[matsumana]

@joao-fontenele I am sorry to bother you. Could you take a look this again?

[joao-fontenele-daitan]

LGTM

[joao-fontenele]

@matsumana there's a conflict with master, if you resolve the conflicts I can merge it

[matsumana]

@joao-fontenele I could not find any conflicts.
According to the following message, seems there is no conflicts.

This branch has no conflicts with the base branch

[joao-fontenele]

yep, my bad I was selecting the option to rebase and merge, and was seeing a conflict, but it's actually updated

[matsumana]

Thank you for reviewing.
Since I would like to use this feature, I would appreciate if you could release the new version.

[joao-fontenele]

@matsumana sorry for the delay, man, and thanks for the contribution.

Already released the new version

[matsumana]

Thank you so much!