Fix constraints bug

[ahorek]

activerecord-sqlserver-adapter (5.2.0)
tiny_tds (2.1.2-x64-mingw32)
rails (5.2.2)

rails migration

change_column :projects, :description, :text, :null => true, :default => nil

raises an error TinyTds::Error: The object 'DF_projects_description' is dependent on column 'description'.

there's a bug in activerecord-sqlserver-adapter that executes commands in wrong order

before

ALTER TABLE table REMOVE CONSTRAINT
ALTER TABLE table ADD CONSTRAINT
ALTER TABLE table ALTER COLUMN

after

ALTER TABLE table REMOVE CONSTRAINT
ALTER TABLE table ALTER COLUMN
ALTER TABLE table ADD CONSTRAINT