Drop {httr} dependency

[jameslamb]

Description

Active development on {httr} stopped 2 years ago.

From its docs:

httr is superseded: only changes necessary to keep it on CRAN will be made. We recommend using httr2 instead.

(r-lib / httr / README.md)

{uptasticsearch} should switch to {httr2} or something else.

Benefits of this work

• reduces the risk of needing to update under thread of CRAN archival if / when {httr} is eventually fully abandoned
• allows {uptasticsearch} to take advantage of whatever improvements {httr2} has over {httr}

Acceptance criteria

• {uptasticsearch} does not depend on {httr}

Approach

We have good tests we can trust, try a change and see what happens.
Choose a replacement that's actively maintained and that hopefully does not introduce too many new dependencies.

Notes

N/A