fix 36666 - Add support for "channel" parameter

This commit introduce the possibility to pass the "channel" parameter to
leapp, so during an upgrade can be targetted release 8.6 EUS, even if
source is 7.9 "plain".

Channels list is take from upstream:
https://github.com/oamg/leapp-repository/blob/84d6ce3073e646e8740b72a5e7edda056c1b324a/commands/preupgrade/__init__.py#L28

ref. https://projects.theforeman.org/issues/36666

README.md

@@ -14,6 +14,14 @@ The plugin will add following jobs:
 - Remediation plan
 - Run upgrade via Leapp
 
+### Channel
+
+Leapp by default will use the same "channel" (e4s, eus, aus) as the current OS, so if you are using "eus" repositories, the target OS will be on "eus" repositories as well.
+But if you are upgrading and want to target a different channel, i.e. from a RHEL 7.9 to a RHEL 8.6 EUS, you can do it by explicitely setting the channel to "eus".
+
+The channel have to be specified in both the preupgrade and upgrade jobs.
+Default value of "channel" is "ga" - General availability: regular repositories are used by default.
+
 ## Api
 - `GET /api/preupgrade_reports` List Preupgrade reports
 - `GET /api/preupgrade_reports/:id` Show Preupgrade report

app/views/foreman_leapp/job_templates/leapp_preupgrade.erb

@@ -6,12 +6,22 @@ description_format: 'Upgradeability check for RHEL host'
 provider_type: SSH
 feature: leapp_preupgrade
 model: JobTemplate
+template_inputs:
+- name: Channel
+  description: Set if the target OS is required to use the General Availability (GA) channel - the default - or a specific channel among: Update Services for SAP Solutions (E4S), Extended Upgrade Support (EUS) or Advanced Update Support (AUS).
+  input_type: user
+  required: true
+  default: "ga"
+  options: "ga\ne4s\neus\naus"
+%>
+<%
+  channel_opts = input('Channel') == 'ga' ? '' : "--channel #{input('Channel')}"
 %>
 
 <%= render_template 'Check Leapp' %>
 
 rm -f /var/log/leapp/leapp-report.json
-leapp preupgrade
+leapp preupgrade <%= channel_opts %>
 
 echo "===leap_upgrade_report_start==="
 cat /var/log/leapp/leapp-report.json

app/views/foreman_leapp/job_templates/leapp_upgrade.erb

@@ -7,6 +7,12 @@ provider_type: Ansible
 feature: leapp_upgrade
 model: JobTemplate
 template_inputs:
+- name: Channel
+  description: Set if the target OS is required to use the General Availability (GA) channel - the default - or a specific channel among: Update Services for SAP Solutions (E4S), Extended Upgrade Support (EUS) or Advanced Update Support (AUS).
+  input_type: user
+  required: true
+  default: "ga"
+  options: "ga\ne4s\neus\naus"
 - name: Reboot
   description: Reboot the host automaticaly to continue with the upgrade
   input_type: user
@@ -16,9 +22,12 @@ template_inputs:
 %>
 ---
 - hosts: all
+  vars:
+    - channel_opts: <% input('Channel') == 'ga' ? '' : "--channel #{input('Channel')}" %>
   tasks:
     - name: Run Leapp Upgrade
-      command: leapp upgrade
+      command: leapp upgrade {{ channel_opts }}
+
 <%- if input('Reboot') == "true" -%>
     - name: Reboot the machine
       reboot: