docs: CrowdStrike Falcon install instructions

caos.ansible_roles/roles/install_crowdstrike_falcon/README.md

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+# CrowdStrike Falcon installer
+
+This role installs the CrowdStrike Falcon sensor in our systems. It uses the installer hashes provided and relates them to each installation method (`dnf`, `apt`, manual, etc). See the [vars](./vars/main.yaml) to see this relation and modify it to your needs (e.g. changing hostnames).
+
+## Providing credentials and variables
+
+This role needs the following credentials to work:
+
+- **CrowdStrike Client ID:** Along with the Client Secret, it will be used to get an auth token to download the appropriate installer. It can be provided to the role setting the `falcon_client_id` variable. 
+- **CrowdStrike Client Secret:** Along with the Client ID, it will be used to get an auth token to download the appropriate installer. It can be provided to the role setting the `falcon_client_secret` variable.
+- **CrowdStrike Customer ID:** It will be used to register the Falcon Sensor installation with CrowdStrike. It can be provided via the `falcon_customer_id` variable.
+
+The URL from where to get the installer is also needed. Set it up via `api_base_url`.
+
+### Passing credentials via the command line
+
+Use the `-e`/`--extra-vars` option to set these variables directly:
+
+```bash
+ansible-playbook -i "$ANSIBLE_INVENTORY" -e "crowdstrike_client_id=$CROWDSTRIKE_CLIENT_ID" -e "crowdstrike_client_secret=$CROWDSTRIKE_CLIENT_SECRET" -e "crowdstrike_customer_id=$CROWDSTRIKE_CUSTOMER_ID" install-requirements.yml
+```
+
+Then, in the `install-requirements.yml` of this example:
+
+```yaml
+- hosts: testing_hosts_linux
+  become: true
+  gather_facts: yes
+  vars:
+    falcon_client_id: "{{ crowdstrike_client_id }}"
+    falcon_client_secret: "{{ crowdstrike_client_secret }}"
+    falcon_customer_id: "{{ crowdstrike_customer_id }}"
+    api_base_url: "https://api.laggar.gcw.crowdstrike.com"
+  tasks:
+    - name: Install CrowdStrike Falcon
+      include_role:
+        name: install-crowdstrike-falcon
+```
+
+### Passing credentials via environment variables
+
+Very similar to the above, but `lookup` directly in the playbook:
+
+```yaml
+- hosts: testing_hosts_linux
+  become: true
+  gather_facts: yes
+  vars:
+    falcon_client_id: "{{ lookup('env', 'CROWDSTRIKE_CLIENT_ID') }}"
+    falcon_client_secret: "{{ lookup('env', 'CROWDSTRIKE_CLIENT_SECRET') }}"
+    falcon_customer_id: "{{ lookup('env', 'CROWDSTRIKE_CUSTOMER_ID') }}"
+    api_base_url: "https://api.laggar.gcw.crowdstrike.com"
+  tasks:
+    - name: Install CrowdStrike Falcon
+      include_role:
+        name: install-crowdstrike-falcon
+```