Deprecate allow_nulls and forbid_nulls since they were duplicated met…

…hods. Fixes #1054

spec/avram/migrator/alter_table_statement_spec.cr

@@ -99,17 +99,6 @@ describe Avram::Migrator::AlterTableStatement do
     built.statements[1].should eq "ALTER TABLE ONLY users ALTER COLUMN id SET DEFAULT '54';"
   end
 
-  it "can change column nullability" do
-    built = Avram::Migrator::AlterTableStatement.new(:users).build do
-      forbid_nulls_for :id
-      allow_nulls_for :age
-    end
-
-    built.statements.size.should eq 2
-    built.statements[0].should eq "ALTER TABLE users ALTER COLUMN id SET NOT NULL;"
-    built.statements[1].should eq "ALTER TABLE users ALTER COLUMN age DROP NOT NULL;"
-  end
-
   describe "fill_existing_with" do
     it "fills existing with value and sets column to be non-null for non-null types" do
       built = Avram::Migrator::AlterTableStatement.new(:users).build do

src/avram/migrator/alter_table_statement.cr

@@ -87,6 +87,7 @@ class Avram::Migrator::AlterTableStatement
   #   allow_nulls_for :email
   # end
   # ```
+  @[Deprecated("Use make_optional instead")]
   macro allow_nulls_for(column_name)
     change_nullability_statements << build_nullability_statement({{column_name.id.stringify}}, true)
   end
@@ -97,6 +98,7 @@ class Avram::Migrator::AlterTableStatement
   #   forbid_nulls_for :email
   # end
   # ```
+  @[Deprecated("Use make_required instead")]
   macro forbid_nulls_for(column_name)
     change_nullability_statements  << build_nullability_statement({{column_name.id.stringify}}, false)
   end