Error if a secret with a newline in it is presented.

I've implemented the logic like this so we can add other "illegal" chars easily if we find them.

manifests/client.pp

@@ -42,6 +42,10 @@ define freeradius::client (
   $fr_basepath = $::freeradius::params::fr_basepath
   $fr_group    = $::freeradius::params::fr_group
 
+  if ($secret !~ /\A[^\n]+\z/) {
+    fail('Secrets cannot have newlines in them')
+  }
+
   file { "${fr_basepath}/clients.d/${shortname}.conf":
     ensure  => $ensure,
     mode    => '0640',

spec/defines/client_spec.rb

@@ -24,4 +24,16 @@ describe 'freeradius::client' do
       .that_requires('File[/etc/raddb/clients.d]')
       .that_requires('Group[radiusd]')
   end
+
+  context 'with secret containing a newline' do
+    let(:params) do
+      super().merge(
+        secret: "foo\nbar",
+      )
+    end
+
+    it do
+      is_expected.to compile.and_raise_error(%r{Secrets cannot have newlines in them})
+    end
+  end
 end