Description:

Generates two new database migrations which will safely add an arbitrary
check constraint and validate it separately.

Example:

rails generate nandi:check_constraint foos baz_or_quux_not_null

This will create:
    db/safe_migrations/20190424123727_add_check_constraint_baz_or_quux_not_null_on_foos.rb
    db/safe_migrations/20190424123728_validate_check_constraint_baz_or_quux_not_null_on_foos.rb

Example:

rails generate nandi:check_constraint foos baz_or_quux_not_null --validation-timeout 20000

This will create:
    db/safe_migrations/20190424123727_add_check_constraint_baz_or_quux_not_null_on_foos.rb
    db/safe_migrations/20190424123728_validate_check_constraint_baz_or_quux_not_null_on_foos.rb

The statement timeout in the second migration will be set to 20,000ms.