Update source_format parameter

Match the possible values to the file suffix of the created source
files.

REFERENCE.md

@@ -1039,7 +1039,7 @@ apt::source { 'puppetlabs':
 
 ```puppet
 apt::source { 'puppetlabs':
-  source_format => 'deb822'
+  source_format => 'sources'
   uris          => ['http://apt.puppetlabs.com'],
   suites        => [$facts['os']['distro']['codename']],
   components    => ['puppet8'],
@@ -1077,11 +1077,11 @@ The following parameters are available in the `apt::source` defined type:
 
 ##### <a name="-apt--source--source_format"></a>`source_format`
 
-Data type: `Enum['legacy', 'deb822']`
+Data type: `Enum['list', 'sources']`
 
 The file format to use for the apt source. See https://wiki.debian.org/SourcesList
 
-Default value: `'legacy'`
+Default value: `'list'`
 
 ##### <a name="-apt--source--location"></a>`location`
 

manifests/source.pp

@@ -23,7 +23,7 @@
 #
 # @example Install the puppetlabs apt source (deb822 format)
 #   apt::source { 'puppetlabs':
-#     source_format => 'deb822'
+#     source_format => 'sources'
 #     uris          => ['http://apt.puppetlabs.com'],
 #     suites        => [$facts['os']['distro']['codename']],
 #     components    => ['puppet8'],
@@ -116,7 +116,7 @@
 #   Specifies whether to check if the package release date is valid. Defaults to `True`.
 #
 define apt::source (
-  Enum['legacy', 'deb822'] $source_format       = 'legacy',
+  Enum['list', 'sources'] $source_format       = 'list',
   Array[Enum['deb','deb-src'], 1, 2] $types     = ['deb'],
   Optional[String] $location                    = undef,
   Optional[Array[String]] $uris                 = undef, # deb822
@@ -145,8 +145,8 @@
   $_before = Apt::Setting["list-${title}"]
 
   case $source_format {
-    'legacy': {
-      $_file_suffix = 'list'
+    'list': {
+      $_file_suffix = $source_format
 
       if !$release {
         if fact('os.distro.codename') {
@@ -292,7 +292,7 @@
         create_resources('apt::pin', { "${name}" => $_pin })
       }
     }
-    'deb822': {
+    'sources': {
       if $pin {
         fail('apt::source::pin parameter is not supported with deb822 format')
       }
@@ -305,7 +305,7 @@
       if !$components {
         fail('You must specify a list of components for the apt::source resource')
       }
-      $_file_suffix = 'sources'
+      $_file_suffix = $source_format
       case $ensure {
         'present': {
           $header = epp('apt/_header.epp')