Allow for new database.yml configurations with roles (#272)

Newer Rails applications may be using a [configuration for multiple
databases](https://guides.rubyonrails.org/active_record_multiple_databases.html).

By default, Rails will look for`primary` named connection details and
use those with multiple db setup. The changes in this PR will look for
and use the `primary` settings if the key exists, otherwise, it will
assume it's normal, single db, database setttings which would be
compatible with previous versions of Rails.

packages/data_taster/lib/data_taster/flavors.rb

@@ -80,7 +80,7 @@ def recent_ids(table_name, col_name)
     end
 
     def source_db
-      @source_db ||= db_config["database"]
+      @source_db ||= db_config[:database]
     end
   end
 end

packages/data_taster/lib/data_taster/helper.rb

@@ -13,12 +13,8 @@ def sanitize_command(command, params = nil)
       sanitized_command
     end
 
-    def db_yml
-      @db_yml ||= YAML.safe_load(ERB.new(Rails.root.join("config", "database.yml").read).result, aliases: true)
-    end
-
     def db_config
-      @db_config ||= db_yml[Rails.env]
+      ActiveRecord::Base.configurations.configs_for(env_name: Rails.env, name: "primary").configuration_hash
     end
 
     def logg(message)