MT#3941 API: Prettify voicemail descriptions.

Properly link between the corresponding collections.

lib/NGCP/Panel/Controller/API/VoicemailRecordings.pm

@@ -20,7 +20,7 @@ class_has 'api_description' => (
     is => 'ro',
     isa => 'Str',
     default => 
-        'Defines the actual recording of voicemail messages. It is referred to by the ngcp:voicemails relation. A GET on an item returns the binary blob of the recording with Content-Type "audio/x-wav".',
+        'Defines the actual recording of voicemail messages. It is referred to by the <a href="#voicemails">Voicemails</a> relation. A GET on an item returns the binary blob of the recording with Content-Type "audio/x-wav".',
 );
 
 with 'NGCP::Panel::Role::API::VoicemailRecordings';

lib/NGCP/Panel/Controller/API/Voicemails.pm

@@ -20,7 +20,7 @@ class_has 'api_description' => (
     is => 'ro',
     isa => 'Str',
     default => 
-        'Defines the meta information like duration, callerid etc for voicemail recordings. The actual recordings can be fetched via the related ngcp:voicemailrecordings relation.',
+        'Defines the meta information like duration, callerid etc for voicemail recordings. The actual recordings can be fetched via the <a href="#voicemailrecordings">VoicemailRecordings</a> relation.',
 );
 
 class_has 'query_params' => (