enhancement - Add support for client certificates when using SSL

[alexanderBendo]

In the current version SSL connections are supported but there is no way to use client certificates. It can be added with something like this in lib/logstash/outputs/mongodb.rb:

   config :ssl_ca_cert, :validate => :string, :required => false                    
   config :ssl_cert, :validate => :string, :required => false                       
   config :ssl_key, :validate => :string, :required => false           

     conn = Mongo::Client.new(@uri,                                                 
       ssl_ca_cert: @ssl_ca_cert,                                                   
       ssl_cert: @ssl_cert,                                                         
       ssl_key: @ssl_key                                                            
     )          

I can submit either a patch or a pull request if you prefer that.

[YakobovLior]

Hey @alexanderBendo, have you tried this in a real plugin?
I've tried to add this to the regular logstash-output-mongodb plugin but no joy.

Thanks,
Lior