CFE-3635: Prototyped dnf_appstream custom promise type

cfbs.json

@@ -223,6 +223,15 @@
         "append enable.cf services/init.cf"
       ]
     },
+    "promise-type-dnf_appstream": {
+      "description": "Promise type to manage dnf appstream modules.",
+      "subdirectory": "promise-types/dnf_appstream",
+      "dependencies": ["library-for-promise-types-in-python"],
+      "steps": [
+        "copy dnf_appstream.py modules/promises/",
+        "append enable.cf services/init.cf"
+      ]
+    },
     "promise-type-git": {
       "description": "Promise type to manage git repos.",
       "subdirectory": "promise-types/git",

promise-types/dnf_appstream/README.md

@@ -0,0 +1,100 @@
+# DNF AppStream Promise Type
+
+A CFEngine custom promise type for managing DNF AppStream modules on compatible systems.
+
+## Overview
+
+The `dnf_appstream` promise type allows you to manage DNF AppStream modules, which are a key feature of RHEL 8+ and compatible systems. AppStreams provide multiple versions of software components that can be enabled or disabled as needed.
+
+## Features
+
+- Enable, disable, install, and remove DNF AppStream modules
+- Support for specifying streams and profiles
+
+## Installation
+
+To install this promise type, copy the `dnf_appstream.py` file to your CFEngine masterfiles directory and configure the promise agent:
+
+```
+promise agent dnf_appstream
+{
+  interpreter => "/usr/bin/python3";
+  path => "$(sys.workdir)/modules/promises/dnf_appstream.py";
+}
+```
+
+## Usage
+
+### Ensure a module is enabled
+
+```
+bundle agent main
+{
+  dnf_appstream:
+      "nodejs"
+        state => "enabled",
+        stream => "12";
+}
+```
+
+### Ensure a module is disabled
+
+```
+bundle agent main
+{
+  dnf_appstream:
+      "nodejs"
+        state => "disabled";
+}
+```
+
+### Ensure a module is installed with a specific profile
+
+```
+bundle agent main
+{
+  dnf_appstream:
+      "python36"
+        state => "installed",
+        stream => "3.6",
+        profile => "minimal";
+}
+```
+
+### Ensure a module is removed
+
+```
+bundle agent main
+{
+  dnf_appstream:
+      "postgresql"
+        state => "removed";
+}
+```
+
+### Reset a module to default
+
+```
+bundle agent main
+{
+  dnf_appstream:
+      "nodejs"
+        state => "default";
+}
+```
+
+## Attributes
+
+The promise type supports the following attributes:
+
+- `state` (optional) - Desired state of the module: `enabled`, `disabled`, `installed`, `removed`, `default`, or `reset` (default: `enabled`)
+- `stream` (optional) - Specific stream of the module to use. Set to `default` to use the module's default stream.
+- `profile` (optional) - Specific profile of the module to install. Set to `default` to use the module stream's default profile.
+
+## Requirements
+
+- CFEngine 3.18 or later
+- Python 3
+- DNF Python API (python3-dnf package)
+- DNF package manager (RHEL 8+, Fedora, CentOS 8+)
+- AppStream repositories configured