Prompted by not being able to tell where a locally-run instance's data dir
actually was without inspecting the running process (ps/lsof). Adds
data_dir to /api/setup/version's response, resolved to an absolute path so
it's unambiguous regardless of whether --data-dir/DATA_DIR was relative or
left at the default.
Shown as a read-only line at the top of the Settings tab, not the always-
visible footer — the footer is prime real estate seen on every tab/every
page load, and this is a rarely-needed piece of diagnostic info that
belongs alongside the rest of System Settings instead.
Also filled in a test-helper gap: the pkg/service/handlers package's
internal test router (main_test.go) never registered /setup/version at
all, unlike the real production router — added it so the new test (and any
future one exercising this endpoint) can actually run.
Unrelated to #419, but found while verifying that work against a running
instance.
Tobias Gesellchen
29463fac98