Override the default user-agent set by httr2 to indicate that a request came from arcgisutils.
Examples
req <- httr2::request("http://example.com")
arc_agent(req)
#> <httr2_request>
#> GET http://example.com
#> Body: empty
#> Options:
#> • useragent: 'arcgisutils v0.3.1'