Can't disable concurrent index creation with Rails 7.1?

[jordan-brough]

In a Rails 7.1 application, if I try to supply algorithm: :default to add_index:

add_index :some_table, [:some_column], algorithm: :default

then I get an error like this:

StandardError: An error has occurred, all later migrations canceled: (StandardError)

Algorithm must be one of the following: :concurrently
ruby/3.3.6/lib/ruby/gems/3.3.0/gems/activerecord-7.1.5.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:1470:in `block in index_algorithm'
ruby/3.3.6/lib/ruby/gems/3.3.0/gems/activerecord-7.1.5.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:1469:in `fetch'

iiuc, Rails is hitting that check & error condition before this safe-pg-migrations code can kick in:

safe-pg-migrations/lib/safe-pg-migrations/plugins/statement_insurer.rb

Lines 56 to 61 in b0efa6d

	def add_index(table_name, column_name, **options)
	if options[:algorithm] == :default
	options.delete :algorithm
	else
	options[:algorithm] = :concurrently
	end

[jordan-brough]

Also interestingly: Supplying algorithm: nil seems to work for remove_index (to disable concurrently) but it doesn't work for add_index (the index is still created concurrently)

[jordan-brough]

Here's a PR with an (untested) change that would allow using algorithm: nil for add_index.
algorithm: nil already works for remove_index.

#155