fix(db): SSL certificates table and model

- server_id is a foreign id
- server_id must be unique as each server can only have 1 CA cert
- resource_id must be unique as each resource can only have 1 SSL cert

app/Models/SslCertificate.php

@@ -11,6 +11,7 @@ class SslCertificate extends Model
         'ssl_private_key',
         'resource_type',
         'resource_id',
+        'server_id',
         'valid_until',
     ];
 
@@ -24,4 +25,9 @@ class SslCertificate extends Model
     {
         return $this->morphTo();
     }
+
+    public function server()
+    {
+        return $this->belongsTo(Server::class);
+    }
 }