biohttp

• tools joins Imports for that call. It ships with R, so it adds nothing to what a consumer installs, and it is declared because R CMD check requires a declaration for anything reached with ::.
• DESCRIPTION gains a reference for the circuit breaker, names the language as en-US, and hyphenates "service-specific".

Fixed

• Every environment variable the package reads now treats an empty export the same way it treats an absent one. Sys.getenv()'s default argument only fires when a name is absent, so a container passing through a variable its operator never filled in got "" rather than the default, and four readers were doing that. env_num() and env_flag() had always had the rule; env_chr() gives it to the rest. The one that mattered was BIOHTTP_CALLER_IDENTITY. Exported empty, it sent User-Agent: biohttp/0.1.2 out as /0.1.2: a version with nothing in front of it, which is the one thing a user agent exists to carry, on a package whose point is being attributable to the service you are calling. Every test in the suite ran that way, because setup.R clears those variables by exporting them empty, and no test looked. BIOHTTP_CACHE_DIR was the same defect with a smaller blast radius: "" as a directory is the working directory, which is what the change above removes. BIOHTTP_CONTACT_URL, BIOHTTP_CONTACT_EMAIL and BIOHTTP_CACHE_SALT all default to "" anyway, so they read the same as before.
• The status_message() example no longer calls withr, which is in Suggests. An example may only use what Imports guarantees: CRAN checks with _R_CHECK_DEPENDS_ONLY_ set, where a Suggests package is simply absent and the example errors. It now sets the option with options() and restores it, which also satisfies the separate rule that an example puts back anything it changes.

Added

• inst/CITATION is shipped, so citation("biohttp") carries the Zenodo DOI from an installed copy. CITATION.cff is in .Rbuildignore and never reached a tarball, so the README had been promising something only a source checkout could deliver. Both exist now, because GitHub's cite box reads the .cff and R reads inst/CITATION.

Documentation

• The README linked to CONTRIBUTING.md and LICENSE.md by relative path. Both are in .Rbuildignore, so neither reaches a tarball and both links were dead for anyone reading the README somewhere other than GitHub, which from here includes the CRAN package page. They are absolute now.
• The README's Imports list named five packages where DESCRIPTION names six. A README that contradicts the DESCRIPTION printed beside it on the CRAN page is worth more than the line it saves.
• The status line no longer carries a version number. The last one went stale within a release of being written, and NEWS.md already answers the question.