With Go 1.26 now released, this bumps the minimum required Go version
from 1.24.11 to 1.25.5 across all go.mod files and updates the
installation documentation with the correct download links and SHA256
hashes for Go 1.25.5 binaries.
The build system (Dockerfiles, Makefile, CI) was already using Go 1.25.5,
so this change aligns the go.mod minimum version to match.
Bump all build go versions to v1.21.0
Bump the minimum build package version to v1.19.0
Debian "buster" is not longer supported. Security updates have been
discontinued since June 30th 2022. We will build using the latest
version, "bookworm".
This commit adds Clock and DefaultClock and moves the private
invoices.testClock under the clock package while adding basic
unit tests for it.
Clock is an interface currently encapsulating Now() and TickAfter().
It can be added as an external dependency to any class. This way
tests can stub out time.Now() or time.After().
The DefaultClock class simply returns the real time.Now() and
time.After().
