Fix rails migration templates for Rails 8

[adamcarlile]

Having just tried to stand this project up in a new Rails 8 application the migration threw a couple of exceptions at me:

-- create_table(:oauth_saml_settings)
bin/rails aborted!
StandardError: An error has occurred, this and all later migrations canceled: (StandardError)

Unknown key: :unique. Valid keys are: :limit, :precision, :scale, :default, :null, :collation, :comment, :primary_key, :if_exists, :if_not_exists, :array, :using, :cast_as, :as, :type, :enum_type, :stored

Related to the missing index method, which then passes the unique constraint as a hash

ArgumentError: you can't redefine the primary key column 'jti' on 'oauth_dpop_proofs'. To define a custom primary key, pass { id: false } to create_table. (ArgumentError)

              raise ArgumentError, "you can't redefine the primary key column '#{name}' on '#{@name}'. To define a custom primary key, pass { id: false } to create_table."

I've changed this to specify id: false in order to allow the manual configuration of the PK