modules: Add a modules directory for mcl code

Details in the README file.

modules/README.md

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+# Modules!
+
+This is a collection of `mcl` modules that may be of general interest.
+
+## Why?
+
+In particular while the project is evolving very rapidly, it makes sense to keep
+these alongside the compiler so that if anything needs refactoring, it happens
+together in the same commit, and if there are improvements made and new features
+added, you can see exactly what commit brought in this change!
+
+## Acceptance criteria
+
+It's sort of arbitrary at the moment, but I'm putting in what I find to be
+generally helpful for my needs. Patches are welcome, but expect I might be a bit
+discerning if it's not what I'm looking for right now.
+
+## Long-term
+
+I see `mgmt` and `mcl` as being able to replace a traditional software
+management daemon, and front-end configuration interface for many projects. As a
+result, it might end up being the de facto way to interact with certain
+services. For example, the `dhcpd` project could decide to provide an mcl module
+as either the primary or secondary interface for managing that service, and in
+that case, it would make sense for that module to live in that source tree.
+
+## Importing?
+
+You can import any of these modules into your `mcl` project with the following
+example for the `purpleidea` module:
+
+```mcl
+import "git://github.com/purpleidea/mgmt/modules/purpleidea/"
+```
+
+## Bugs, questions, thanks?
+
+Reach out and let us know!

modules/purpleidea/main.mcl

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+# Mgmt
+# Copyright (C) 2013-2024+ James Shubin and the project contributors
+# Written by James Shubin <james@shubin.ca> and the project contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+# Additional permission under GNU GPL version 3 section 7
+#
+# If you modify this program, or any covered work, by linking or combining it
+# with embedded mcl code and modules (and that the embedded mcl code and
+# modules which link with this program, contain a copy of their source code in
+# the authoritative form) containing parts covered by the terms of any other
+# license, the licensors of this program grant you additional permission to
+# convey the resulting work. Furthermore, the licensors of this program grant
+# the original author, James Shubin, additional permission to update this
+# additional permission if he deems it necessary to achieve the goals of this
+# additional permission.
+
+import "os"
+
+# base contains the personal tweaks and utilities of james (purpleidea)
+class base() {
+	if os.is_redhat() {
+		pkg [
+			"ack",
+			"bash-completion",
+			"direnv",
+			"fping",
+			"git",
+			"htop",
+			"lshw",
+			"nethogs",
+			"nmap",
+			"screen",
+			"socat",
+			"strace",
+			"telnet",
+			"tree",
+			"vim-enhanced",
+			"wget2-wget",
+		] {
+			state => "installed",
+		}
+	}
+	if os.is_debian() {
+		pkg [
+			"ack",
+			"bash-completion",
+			"direnv",
+			"fping",
+			"git",
+			"htop",
+			"lshw",
+			"nethogs",
+			"nmap",
+			"screen",
+			"socat",
+			"strace",
+			"telnet",
+			"tree",
+			"vim",
+			"wget",
+		] {
+			state => "installed",
+		}
+	}
+}

test/test-modules.sh

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+#!/bin/bash
+# check that our modules still build, even if we don't run them here
+
+# shellcheck disable=SC1091
+. test/util.sh
+
+echo running "$0"
+
+ROOT=$(dirname "${BASH_SOURCE}")/..
+cd "${ROOT}"
+
+failures=''
+
+# Test modules/ directory to see if the .mcl files compile correctly.
+
+find_mcl_modules() {
+	git ls-files | grep '\.mcl$' | grep '^modules/' | grep -v 'examples/lang/'
+}
+
+# TODO: It might be better to only test from the root module entrypoint.
+for file in $(find_mcl_modules); do
+	#echo "mcl: $file"
+	run-test ./mgmt run --tmp-prefix lang --only-unify "$file" &> /dev/null || fail_test "could not compile: $file"
+done
+
+if [[ -n "$failures" ]]; then
+	echo 'FAIL'
+	echo "The following tests (in: ${linkto}) have failed:"
+	echo -e "$failures"
+	echo
+	exit 1
+fi
+echo 'PASS'