Make list of SASL mechanisms configurable

Author: dominikh

docs/bot_options.md

@@ -320,6 +320,17 @@ Default value
 Description
 : The password to use for SASL authentication.
 
+### sasl.mechanisms
+Type
+: Array<Cinch::SASL::Mechanism>
+
+Default value
+: `[Cinch::SASL::DH_Blowfish, Cinch::SASL::Plain]`
+
+Description
+: The SASL mechanisms to use. All mechanisms in the array will be
+attempted, until one was successful
+
 ## server
 Type
 : String

lib/cinch/configuration/sasl.rb

@@ -1,15 +1,17 @@
 require "cinch/configuration"
+require "cinch/sasl"
 
 module Cinch
   class Configuration
     # @since 2.0.0
     class SASL < Configuration
-      KnownOptions = [:username, :password]
+      KnownOptions = [:username, :password, :mechanisms]
 
       def self.default_config
         {
           :username => nil,
           :password => nil,
+          :mechanisms => [Cinch::SASL::DH_Blowfish, Cinch::SASL::Plain]
         }
       end
     end

lib/cinch/irc.rb

@@ -210,7 +210,7 @@ def send_sasl
     def start
       setup
       if connect
-        @sasl_remaining_methods = [SASL::Plain, SASL::DH_Blowfish]
+        @sasl_remaining_methods = @bot.config.sasl.mechanisms.reverse
         send_cap_ls
         send_login