The intention is to keep to repo root clean while the list of packages
is slowly growing.
Additionally, a bunch of small (~30 LoC) files in the repo root is
merged into a single maddy.go file, for the same reason.
Most of the internal code is moved into the internal/ directory. Go
toolchain will make it impossible to import these packages from external
applications.
Some packages are renamed and moved into the pkg/ directory in the root.
According to https://github.com/golang-standards/project-layout this is
the de-facto standard to place "library code that's ok to use by
external applications" in.
To clearly define the purpose of top-level directories, README.md files
are added to each.
It has all sorts of benefits due to the service manager being aware of
the starting/running/stopping state, see systemd.service(5)
On top of that, start-up errors are reported using STATUS= key, so they
will be easier to see in the 'systemctl status' output.
To support unusual configuration syntax, endpoint modules (imap, smtp,
etc) relied on rather awkward code using modName+instName+aliases as
arguments. This commit replaces old handling with use of special
signature similar to inlineArgs introduced in 1edd031.
Endpoint modules are placed in a separate 'registry' and use
different initialization callback signature for simplicity. This makes
them inaccessible for other modules, though they are not supposed to be
anyway.
Endpoint modules are initialized before other modules. This allows
detecting unused configuration blocks by checking for modules
that were not lazily initalized after endpoint initialization.
This relies on endpoint modules being essentially "roots" of
instances dependency tree.
Idea of "semantical module names" is completely dropped now and so
HACKING.md is updated to not mention it.
