Move token availability checking to its own method for easier overriding

app/models/passwordless/session.rb

@@ -61,16 +61,20 @@ def available?
 
  private
 
+ def token_digest_available?(token_digest)
+ Session.available.where(token_digest: token_digest).none?
+ end
+
  def set_defaults
  self.expires_at ||= Passwordless.expires_at.call
  self.timeout_at ||= Passwordless.timeout_at.call
 
- return if self.token || self.token_digest
+ return if self.token_digest
 
  self.token, self.token_digest = loop {
  token = Passwordless.token_generator.call(self)
  digest = Passwordless.digest(token)
- break [token, digest] unless Session.find_by(token_digest: digest)
+ break [token, digest] if token_digest_available?(digest)
  }
  end
  end