New hostgroup management module

There is a new hostgroup management module placed in the plugins folder:

  plugins/modules/ipahostgroup.py

The hostgroup module allows to add, remove and disable hosts.

The hostgroup module is as compatible as possible to the Ansible upstream
ipa_hostgroup module, but addtionally offers to ensure member presence and
absence.

Here is the documentation for the module:

  README-hostgroup.md

New example playbooks have been added:

  playbooks/hostgroup/ensure-hostgroup-is-absent.yml
  playbooks/hostgroup/ensure-hostgroup-is-present.yml
  playbooks/hostgroup/ensure-hosts-and-hostgroups-are-absent-in-hostgroup.yml
  playbooks/hostgroup/ensure-hosts-and-hostgroups-are-present-in-hostgroup.yml

README-hostgroup.md

@@ -0,0 +1,147 @@
+Hostgroup module
+================
+
+Description
+-----------
+
+The hostgroup module allows to ensure presence and absence of hostgroups and members of hostgroups.
+
+The hostgroup module is as compatible as possible to the Ansible upstream `ipa_hostgroup` module, but addtionally offers to make sure that hosts are present or absent in a hostgroup.
+
+
+Features
+--------
+* Hostgroup management
+
+
+Supported FreeIPA Versions
+--------------------------
+
+FreeIPA versions 4.4.0 and up are supported by the ipahostgroup module.
+
+
+Requirements
+------------
+
+**Controller**
+* Ansible version: 2.8+
+
+**Node**
+* Supported FreeIPA version (see above)
+
+
+Usage
+=====
+
+Example inventory file
+
+```ini
+[ipaserver]
+ipaserver.test.local
+```
+
+
+Example playbook to make sure hostgroup databases exists:
+
+```yaml
+---
+- name: Playbook to handle hostgroups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  # Ensure host-group databases is present
+  - ipahostgroup:
+      ipaadmin_password: MyPassword123
+      name: databases
+      host:
+      - db.example.com
+      hostgroup:
+      - mysql-server
+      - oracle-server
+```
+
+Example playbook to make sure that hosts and hostgroups are present in existing databases hostgroup:
+
+```yaml
+---
+- name: Playbook to handle hostgroups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  # Ensure hosts and hostgroups are present in existing databases hostgroup
+  - ipahostgroup:
+      ipaadmin_password: MyPassword123
+      name: databases
+      host:
+      - db.example.com
+      hostgroup:
+      - mysql-server
+      - oracle-server
+      action: member
+```
+`action` controls if a the hostgroup or member will be handled. To add or remove members, set `action` to `member`.
+
+Example playbook to make sure hosts and hostgroups are absent in databases hostgroup:
+
+```yaml
+---
+- name: Playbook to handle hostgroups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  # Ensure hosts and hostgroups are absent in databases hostgroup
+  - ipahostgroup:
+      ipaadmin_password: MyPassword123
+      name: databases
+      host:
+      - db.example.com
+      hostgroup:
+      - mysql-server
+      - oracle-server
+      action: member
+      state: absent
+```
+
+Example playbook to make sure host-group databases is absent:
+
+```yaml
+---
+- name: Playbook to handle hostgroups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  # Ensure host-group databases is absent
+  - ipahostgroup:
+      ipaadmin_password: MyPassword123
+      name: databases
+      state: absent
+```
+
+
+Variables
+=========
+
+ipahostgroup
+-------
+
+Variable | Description | Required
+-------- | ----------- | --------
+`ipaadmin_principal` | The admin principal is a string and defaults to `admin` | no
+`ipaadmin_password` | The admin password is a string and is required if there is no admin ticket available on the node | no
+`name` \| `cn` | The list of hostgroup name strings. | no
+`description` | The hostgroup description string. | no
+`nomembers` | Suppress processing of membership attributes. (bool) | no
+`host` | List of host name strings assigned to this hostgroup. | no
+`hostgroup` | List of hostgroup name strings assigned to this hostgroup. | no
+`action` | Work on hostgroup or member level. It can be on of `member` or `hostgroup` and defaults to `hostgroup`. | no
+`state` | The state to ensure. It can be one of `present` or `absent`, default: `present`. | no
+
+
+Authors
+=======
+
+Thomas Woerner