Use schema auto-infer

Ref: rom-rb/rom#345
Ref: rom-rb/rom-sql#63

lib/hanami/entity.rb

@@ -72,6 +72,11 @@ def ==(other)
         id == other.id
     end
 
+    def to_h
+      @attributes.dup
+    end
+    alias_method :to_hash, :to_h
+
     private
 
     attr_reader :attributes

test/integration/repository_test.rb

@@ -120,7 +120,7 @@
       found = repository.find_with_comments(user.id)
 
       found.must_equal user
-      found.comments.must_equal [comment]
+      found.comments.map(&:to_h).must_equal [comment.to_h]
     end
   end
 end

test/support/fixtures.rb

@@ -28,10 +28,7 @@ class Comment
 
 class UserRepository < Hanami::Repository
   relation(:users) do
-    schema do
-      attribute :id, ROM::SQL::Types::Serial # We can copy these types to Hanami
-      attribute :name, ROM::SQL::Types::String # We can copy these types to Hanami
-
+    schema(infer: true) do
       associate do
         many :comments
       end
@@ -66,11 +63,7 @@ def find_with_comments(id)
 
 class CommentRepository < Hanami::Repository
   relation(:comments) do
-    schema do
-      attribute :id, ROM::SQL::Types::Serial # We can copy these types to Hanami
-      attribute :user_id, ROM::SQL::Types::ForeignKey(:users) # We can copy these types to Hanami
-      attribute :text, ROM::SQL::Types::String # We can copy these types to Hanami
-    end
+    schema(infer: true)
 
     def by_id(id)
       where(id: id)