Rename AssociationMatcher#join_table

Free up the `join_table` name so that users can specify a `join_table`
option when testing their associations.

lib/shoulda/matchers/active_record/association_matcher.rb

@@ -823,7 +823,7 @@ module Shoulda
       # @private
       class AssociationMatcher
         delegate :reflection, :model_class, :associated_class, :through?,
-          :join_table, :polymorphic?, to: :reflector
+          :join_table_name, :polymorphic?, to: :reflector
 
         def initialize(macro, name)
           @macro = macro

lib/shoulda/matchers/active_record/association_matchers/join_table_matcher.rb

@@ -8,7 +8,7 @@ module Shoulda
 
           alias :missing_option :failure_message
 
-          delegate :model_class, :join_table, :associated_class,
+          delegate :model_class, :join_table_name, :associated_class,
             to: :association_matcher
 
           delegate :connection, to: :model_class
@@ -24,7 +24,7 @@ module Shoulda
           end
 
           def join_table_exists?
-            if connection.tables.include?(join_table)
+            if connection.tables.include?(join_table_name)
               true
             else
               @failure_message = missing_table_message
@@ -60,16 +60,16 @@ module Shoulda
           end
 
           def actual_join_table_columns
-            connection.columns(join_table).map(&:name)
+            connection.columns(join_table_name).map(&:name)
           end
 
           def missing_table_message
-            "join table #{join_table} doesn't exist"
+            "join table #{join_table_name} doesn't exist"
           end
 
           def missing_columns_message
             missing = missing_columns.join(', ')
-            "join table #{join_table} missing #{column_label}: #{missing}"
+            "join table #{join_table_name} missing #{column_label}: #{missing}"
           end
 
           def column_label

lib/shoulda/matchers/active_record/association_matchers/model_reflection.rb

@@ -24,15 +24,15 @@ module Shoulda
             reflection.options[:through]
           end
 
-          def join_table
-            join_table =
+          def join_table_name
+            join_table_name =
               if has_and_belongs_to_many_name_table_name
                 has_and_belongs_to_many_name_table_name
               else
                 reflection.join_table
               end
 
-            join_table.to_s
+            join_table_name.to_s
           end
 
           def association_relation

lib/shoulda/matchers/active_record/association_matchers/model_reflector.rb

@@ -4,7 +4,7 @@ module Shoulda
       module AssociationMatchers
         # @private
         class ModelReflector
-          delegate :associated_class, :through?, :join_table,
+          delegate :associated_class, :through?, :join_table_name,
             :association_relation, :polymorphic?, :foreign_key,
             :association_foreign_key, to: :reflection