stages/cloud-init: write only one config file

Instead of supporting writing an arbitrary number of configuration
files, just write one. This makes the stage and its schema clearer
and simpler. If more than one config file is needed, the stage can
be repeated multiple times. It is also more flexible since we can
in the future specify the directory, `/etc` vs `/usr` via a new
top level `directory` key.

stages/org.osbuild.cloud-init

@@ -2,18 +2,12 @@
 """
 Configure cloud-init
 
-The 'config' option allows to create cloud-init `.cfg` configuration
-files under `/etc/cloud/cloud.cfg.d`. Its value is a dictionary which keys
-represent filenames of `.cfg` configuration files, which will be created.
-Value of each configuration file key is a dictionary representing the
-cloud-init configuration.
+The 'config' option allows to configure cloud-init by creating a
+configuration file under `/etc/cloud/cloud.cfg.d` with the name
+specified by `filename`.
 
 Constrains:
-  - If 'config' option is specified, it must contain at least one definition
-    of a configuration file.
   - Each configuration file definition must contain at least one configuration
-    section definition, which is not empty (must be setting a configuration
-    option).
 
 Currently supported subset of cloud-init configuration:
   - 'system_info' section
@@ -31,36 +25,33 @@ import osbuild.api
 
 SCHEMA = r"""
 "additionalProperties": false,
+"required": ["config", "filename"],
 "properties": {
+  "filename": {
+    "type": "string",
+    "description": "Name of the cloud-init configuration file.",
+    "pattern": "^[\\w.-]{1,251}\\.cfg$"
+  },
   "config": {
     "additionalProperties": false,
     "type": "object",
-    "description": "cloud-init configuration file.",
-    "minProperties": 1,
-    "patternProperties": {
-      "^[\\w.-]{1,251}\\.cfg$": {
+    "description": "cloud-init configuration",
+    "properties": {
+      "system_info": {
         "additionalProperties": false,
         "type": "object",
-        "description": "cloud-init configuration file.",
+        "description": "'system_info' configuration section.",
         "minProperties": 1,
         "properties": {
-          "system_info": {
+          "default_user": {
             "additionalProperties": false,
             "type": "object",
-            "description": "'system_info' configuration section.",
+            "description": "Configuration of the 'default' user created by cloud-init.",
             "minProperties": 1,
             "properties": {
-              "default_user": {
-                "additionalProperties": false,
-                "type": "object",
-                "description": "Configuration of the 'default' user created by cloud-init.",
-                "minProperties": 1,
-                "properties": {
-                  "name": {
-                    "type": "string",
-                    "description": "username of the 'default' user."
-                  }
-                }
+              "name": {
+                "type": "string",
+                "description": "username of the 'default' user."
               }
             }
           }
@@ -72,20 +63,16 @@ SCHEMA = r"""
 """
 
 
-# Writes the passed `options` object as is into the configuration file in YAML format.
-# The validity of the `options` content is assured by the SCHEMA.
-def create_configuration_file(tree, filename, options):
+# Writes the passed `config` object as is into the configuration file in YAML format.
+# The validity of the `config` content is assured by the SCHEMA.
+def main(tree, options):
+    filename = options.get("filename")
+    config = options.get("config", {})
+
     config_files_dir = f"{tree}/etc/cloud/cloud.cfg.d"
 
     with open(f"{config_files_dir}/{filename}", "w") as f:
-        yaml.dump(options, f)
-
-
-def main(tree, options):
-    configuration_files_options = options.get("config", {})
-
-    for configuration_file, configuration_options in configuration_files_options.items():
-        create_configuration_file(tree, configuration_file, configuration_options)
+        yaml.dump(config, f)
 
     return 0
 

test/data/stages/cloud-init/b.json

@@ -506,12 +506,11 @@
       {
         "name": "org.osbuild.cloud-init",
         "options": {
+          "filename": "00-default_user.cfg",
           "config": {
-            "00-default_user.cfg": {
-              "system_info": {
-                "default_user": {
-                  "name": "ec2-user"
-                }
+            "system_info": {
+              "default_user": {
+                "name": "ec2-user"
               }
             }
           }

test/data/stages/cloud-init/b.mpp.json

@@ -32,12 +32,11 @@
       {
         "name": "org.osbuild.cloud-init",
         "options": {
+          "filename": "00-default_user.cfg",
           "config": {
-            "00-default_user.cfg": {
-              "system_info": {
-                "default_user": {
-                  "name": "ec2-user"
-                }
+            "system_info": {
+              "default_user": {
+                "name": "ec2-user"
               }
             }
           }