fix: restore req body

[sigua-cs]

Description

Fix restore original req.Body ## Pull request type implements https://github.com/ContentSquare/chproxy/issues/336 Please check the type of change your PR introduces: - [x] Bugfix - [ ] Feature - [ ] Code style update (formatting, renaming) - [ ] Refactoring (no functional changes, no api changes) - [ ] Build related changes - [ ] Documentation content changes - [ ] Other (please describe): ### Checklist - [ ] Linter passes correctly - [ ] Add tests which fail without the change (if possible) - [ ] All tests passing - [ ] Extended the README / documentation, if necessary ## Does this introduce a breaking change?

• [ ] Yes
• [ ] No

Further comments

[render[bot]]

Your Render PR Server URL is https://chproxy-pr-397.onrender.com.

Follow its progress at https://dashboard.render.com/static/srv-cmv26nv109ks739iu2t0.

[sigua-cs]

Is there an easy way to add a test in order to assess the before/after change behavior (to ensure we don't have a regression in the future)?

I'll try