add connection plugin for buildah (#26170)

* add connection plugin for buildah

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

* fixup

 * create a method to invoke buildah
 * mount container filesystem persistently so we can access it
   during put and fetch
 * use copyfile function for copying files

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

* revert tests

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

* fixup

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

* progress

(this will be squashed into a single commit before merge)

 * add docs for the conn plugin
 * fix issue invoking the integration tests
 * add a way to invoke commands inside the container as a different user

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

* fix shellcheck warning

Signed-off-by: Tomas Tomecek <ttomecek@redhat.com>

test/integration/connection-buildah.yaml

@@ -0,0 +1,5 @@
+- hosts: buildah-container
+  connection: buildah
+  gather_facts: no
+  roles:
+    - { role: connection_buildah }

test/integration/targets/connection_buildah/aliases

@@ -0,0 +1 @@
+needs/root

test/integration/targets/connection_buildah/posix.sh

@@ -0,0 +1 @@
+../connection_posix/test.sh

test/integration/targets/connection_buildah/runme.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+set -eux
+
+ANSIBLE_TEST_REMOTE_INTERPRETER='' ./posix.sh "$@"
+
+ANSIBLE_TEST_REMOTE_INTERPRETER='' ANSIBLE_REMOTE_USER="1000" ./posix.sh "$@"

test/integration/targets/connection_buildah/test_connection.inventory

@@ -0,0 +1,12 @@
+[buildah]
+buildah-container    ansible_ssh_pipelining=true
+[buildah:vars]
+# 1. install buildah
+# 2. create container:
+# $ sudo buildah from --name=buildah-container python:2
+# 3. run test:
+# $ ANSIBLE_TEST_REMOTE_INTERPRETER= ansible-test integration --local connection_buildah
+# 6. remove container
+# $ sudo buildah rm buildah-container
+ansible_host=buildah-container
+ansible_connection=buildah