Deprecate rhn_channel & rhn_register (#6493)

They are useful only with RHN, which Red Hat discontinued many years
ago, and with Spacewalk 5, which is EOL for more than 3 years;
while they could be potentially used with Uyuni / SUSE Manager (fork of
Spacewalk 5), we have not heard about anyone using it in those setups.

Hence, deprecate these two modules, with their removal planned for
10.0.0 in case there are no reports about being still useful, and
potentially noone that steps up to maintain them.

changelogs/fragments/6493-deprecate-rhn-modules.yml

@@ -0,0 +1,10 @@
+deprecated_features:
+  - |
+    rhn_channel, rhn_register - RHN hosted at redhat.com was discontinued years
+    ago, and Spacewalk 5 (which uses RHN) is EOL since 2020, May 31st;
+    while these modules could work on Uyuni / SUSE Manager (fork of Spacewalk 5),
+    we have not heard about anyone using them in those setups. Hence, these
+    modules are deprecated, and will be removed in community.general 10.0.0
+    in case there are no reports about being still useful, and potentially
+    noone that steps up to maintain them
+    (https://github.com/ansible-collections/community.general/pull/6493).

meta/runtime.yml

@@ -126,6 +126,16 @@ plugin_routing:
       deprecation:
         removal_version: 9.0.0
         warning_text: This module relies on the deprecated package pyrax.
+    rhn_channel:
+      deprecation:
+        removal_version: 10.0.0
+        warning_text: RHN is EOL, please contact the community.general maintainers
+          if still using this; see the module documentation for more details.
+    rhn_register:
+      deprecation:
+        removal_version: 10.0.0
+        warning_text: RHN is EOL, please contact the community.general maintainers
+          if still using this; see the module documentation for more details.
     database.aerospike.aerospike_migrations:
       redirect: community.general.aerospike_migrations
       deprecation:

plugins/modules/rhn_channel.py

@@ -67,6 +67,16 @@ options:
         type: bool
         default: true
         version_added: '0.2.0'
+deprecated:
+    removed_in: 10.0.0
+    why: |
+      RHN hosted at redhat.com was discontinued years ago, and Spacewalk 5
+      (which uses RHN) is EOL since 2020, May 31st; while this module could
+      work on Uyuni / SUSE Manager (fork of Spacewalk 5), we have not heard
+      about anyone using it in those setups.
+    alternative: |
+      Contact the community.general maintainers to report the usage of this
+      module, and potentially step up to maintain it.
 '''
 
 EXAMPLES = '''

plugins/modules/rhn_register.py

@@ -88,6 +88,16 @@ options:
             - If C(true), the registered node will not upload its installed packages information to Satellite server.
         type: bool
         default: false
+deprecated:
+    removed_in: 10.0.0
+    why: |
+      RHN hosted at redhat.com was discontinued years ago, and Spacewalk 5
+      (which uses RHN) is EOL since 2020, May 31st; while this module could
+      work on Uyuni / SUSE Manager (fork of Spacewalk 5), we have not heard
+      about anyone using it in those setups.
+    alternative: |
+      Contact the community.general maintainers to report the usage of this
+      module, and potentially step up to maintain it.
 '''
 
 EXAMPLES = r'''