i-1 Introduces an Ansible playbook for linux-container with SSH access

# Issue

This PR implements the following [issue](the-liberated-edge/test-linux-containers#1).

# Acceptance criteria

- [x] A playbook for launching LXD Debian container with parameterized container name and OS version has been implemented.
- [x] The newly launched Linux containers can be connected to and administered via SSH.
- [x] The playbook has been part of an Ansible collection named theliberatededge.test_linux_containers.
- [x] Setup and getting started technical documentation has been added to README.md.

Co-authored-by: emo <esimeonov@gmail.com>
Reviewed-on: #2

roles/linux_container/tasks/openssh-server.yml

@@ -0,0 +1,74 @@
+---
+- name: find systemctl service for openssh-server
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          systemctl status ssh.service
+  register: ssh_service
+  changed_when: false
+  failed_when: false
+- name: set fact ssh_service_exists
+  ansible.builtin.set_fact:
+    ssh_service_exists: '{{ ssh_service.rc == 0 }}'
+- name: install system package openssh-server
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          apt install -y openssh-server
+  register: ssh_pkg
+  when: not ssh_service_exists
+- name: check openssh server configuration for root access
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          grep -e "^PermitRootLogin yes$" /etc/ssh/sshd_config
+  register: root_access
+  changed_when: false
+  failed_when: false
+- name: set fact ssh_root_login_allowed
+  ansible.builtin.set_fact:
+    ssh_root_login_allowed: '{{ root_access.rc == 0 }}'
+- name: configure openssh server to allow root access via ssh
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          sed -i "$ a PermitRootLogin yes" /etc/ssh/sshd_config
+  register: sshd_config
+  when: not ssh_root_login_allowed
+- name: set fact ssh_server_installed
+  ansible.builtin.set_fact:
+    ssh_pkg_installed: '{{ ssh_pkg.changed and ssh_pkg.rc == 0 }}'
+- name: enable openssh server systemd service
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          systemctl enable --now ssh.service
+  when: ssh_pkg_installed
+- name: set fact sshd_config_touched
+  ansible.builtin.set_fact:
+    sshd_config_touched: '{{ sshd_config.changed and sshd_config.rc == 0 }}'
+- name: restart openssh server systemd service
+  ansible.builtin.shell:
+    cmd: |-
+      lxc exec {{ lte_container_name }} -- \
+          systemctl restart ssh.service
+  when: sshd_config_touched
+- name: find container ip address
+  ansible.builtin.command: lxc ls -c=4 -f=compact {{ lte_container_name }}
+  register: ipv4
+  changed_when: false
+  when: sshd_config_touched
+- name: set fact ipv4
+  ansible.builtin.set_fact:
+    ipv4: '{{ ipv4.stdout_lines[1] }}'
+  when: sshd_config_touched
+- name: extract ipv4 address of the linux container
+  ansible.builtin.set_fact:
+    ipv4: "{{ ipv4 | regex_search('([0-9]+.[0-9]+.[0-9]+.[0-9]+)') }}"
+  when: sshd_config_touched
+- name: ssh-copy-id from server on the Edge to linux container
+  ansible.builtin.shell:
+    cmd: |-
+      sshpass -p {{ lte_container_root_pwd }} \
+          ssh-copy-id -o StrictHostKeyChecking=no root@{{ ipv4 }}
+  when: sshd_config_touched